Short-Range Order Enhances Strength and Tensile Ductility in Nanocrystalline Silver with Intercalation of Amorphous Nickel Nanolayers

Short-Range Order Enhances Strength and Tensile Ductility in Nanocrystalline Silver with Intercalation of Amorphous Nickel Nanolayers | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Article Short-Range Order Enhances Strength and Tensile Ductility in Nanocrystalline Silver with Intercalation of Amorphous Nickel Nanolayers Frederic Sansoz, Malcolm Pringle, Jin-Su Oh, Lin Zhou, Ryan Ott, and 3 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-4402670/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Silver, known for its high thermal and electrical conductivity, is an ideal metal for thin-film electrode applications. Because alloying can negatively affect conductivity, enhancing the strength and resistance to strain poses a tremendous challenge when applied to pure Ag films. Herein, in both experiments and atomistic simulations, we discover a nanoscale strengthening mechanism by intercalating ultrathin amorphous Ni-rich layers between pure nanocrystalline Ag films, resulting in the formation of a multilayered Ag and Ni-Ag alloy material with a stable grain size (22 nm) combining the highest hardness (2.6 GPa), tensile strength (677 MPa) and plastic elongation (6.6%) ever reported for this metal. The integration of amorphous Ni-Ag alloy nanolayers substantially improves the strain hardening behavior and extends the tensile ductility compared to standard crystalline Ag/Ni nanolaminates at an equivalent Ag layer thickness. This phenomenon results from strain-induced chemical short-range order within the amorphous Ni-Ag nanolayers during plastic deformation. The new nanoscale strengthening mechanism can be easily leveraged to develop nanocrystalline films with exceptional mechanical and physical properties. Physical sciences/Materials science/Structural materials/Mechanical properties Physical sciences/Nanoscience and technology/Nanoscale materials Short-range order hardening tensile ductility nanocrystalline metals multilayers. Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Introduction Regarding its high electrical conductivity 1 , Ag is a reference metal against which other materials are generally tested. Utilizing pure Ag over Ag alloys has clear advantages for improving thermal and electrical performances 2,3 and is of practical importance for conductive film electrodes in flexible devices 4-7 . Despite this quality, the low strength and extreme softness of a pure Ag metal imposes significant limitations for deformable films and coatings. Two common methods for enhancing strength and hardness in pure metal films are nanoscale grain refinement and nanolayer structuring. Yet these methods present unresolved challenges when applied to pure Ag films. The first approach for strengthening crystalline films is to reduce the average grain diameter to leverage grain-boundary effects associated with Hall-Petch hardening mechanisms 8-10 . Regardless of its potential benefits, this approach leads to a severe loss of strain hardening and tensile elongation 11,12 , due to strain localization and cracking mechanisms at the interfaces 13-16 . Furthermore, there is a maximum strength limit at which nanocrystalline materials become softer as the grain size decreases at the nanoscale, known as Hall-Petch breakdown, caused by intergranular plastic deformation from the high grain-boundary density 17,18 . Previous atomistic simulations have suggested that the optimal grain size for maximum hardness in pure Ag is in the 16-20 nm range 19 , but achieving this size experimentally is difficult due to the high instability of pure nanosized Ag grains 20 . The smallest stable grain size of pure face-centered cubic (FCC) Ag made by magnetron sputtering was 150 nm 21 . To stabilize the grain size and twin spacing in FCC Ag, adding small concentrations of solute atoms to the grain boundaries can be effective; for example, nanocrystalline Ag films doped with trace amounts of Cu have a stable grain size down to 50 nm 3 . Introducing higher solute concentrations can negatively impact the high thermal and electrical conductivity of Ag crystals 22 . However, conductivity remains high when adding high amounts of Cu in multilayered Ag/Cu materials 23 . The second strengthening approach is by deposition of alternating nanoscale crystalline-amorphous layers of variable thickness 24-26 . Crystalline nanolayers have unique strain hardening mechanisms due to the amount of stress required to move lattice dislocations across parallel interfaces 27,28 . Additionally, crystalline-amorphous nanolaminates are strengthened by the special interface structure between crystalline and amorphous layers and the obstacle formed by the amorphous layers to the propagation of slip bands 24 . All evidence proves that prolonging the tensile ductility under plastic deformation requires materials to exhibit more strain hardening. However, strain-hardening was absent in nanolayered crystalline-amorphous Cu-Zr films 24,25,29 , because incorporating non-crystalline layers to crystalline films gave rise to a transition from hardening to softening behavior 25 and brittle cracking 29 . In this article, we report experiments and atomistic simulations on nanocrystalline Ag films with maximum hardness and strain hardening characteristics obtained by intercalating nanoscale amorphous Ni-rich layers at a crystalline-to-amorphous thickness ratio of 0.1. The choice for ultrathin amorphous Ni layers is important in several aspects. First, past experimental studies 24,30 have shown that reducing the thickness of amorphous layers to a few nanometers is beneficial for reclaiming some tensile plastic elongation in nanolaminates, because thinner layers can serve as both sink and source for lattice dislocations similarly to grain boundaries. In fact, an experimental study on nanocrystalline Ag/amorphous Cu-Zr nanolaminates found that the critical strain before fracture could be maximized at a thickness ratio of 0.1, although the underlying deformation mechanism was dominated by cracking of the amorphous Cu-Zr layers 29,30 . Second, Ag and Ni are immiscible, resulting in heterogeneous Ni phase separation and clustering at interfaces in nanocrystalline FCC Ag, which helps with the stability of ultrathin Ni layers 31-34 and should yield intriguing deformation mechanisms that have not been fully explored so far. Third, the defined thickness between amorphous nanolayers can control the grain size, thereby providing a viable solution for stabilizing nanograins in pure Ag at the maximum Hall-Petch strength limit 19 . Results and Discussion We synthesized a nanocrystalline Ag foil intercalated with ultrathin Ni layers by magnetron sputtering (see Methods). The foil was 3.2 mm in total thickness and composed of alternating pure nanocrystalline Ag and thin Ni layers of 23.6 ± 0.5 nm and 2.5 ± 0.3 nm in thickness, respectively, as shown by transmission electron microscopy (TEM) in Figure 1(a). Although the thickness was found to be uniform within one nanolayer, some Ni nanolayers could be found to be 1-2 nm thicker than others (Supplementary Figure S1). The Ni nanolayer structure was amorphous, as evidenced by the absence of crystal Ni peaks in the electron diffraction in Figures 1(b)-(c) and the atomic-scale high-angle angular dark-field (HAADF) scanning transmission electron microscopy (STEM) in Figures 1(d)-(f). Each Ag layer was made of equiaxed grains with an average diameter of ~22 nm indicating that the grain size of these films depends on the Ag layer thickness, which is consistent with similarly synthesized nanolaminates in the literature. This corresponds to the smallest grain size ever recorded for sputtered pure Ag materials, suggesting that the intercalation of amorphous Ni nanolayers between nanocrystalline Ag films improved microstructure stability during sputtering deposition. Further evidence for the exceptional grain stability of intercalated nanocrystalline Ag layers during plastic deformation experiments is presented below. Furthermore, the material contained some intragranular nanoscale twins (Supplementary Figure S1). A twin boundary is a coherent crystalline interface with perfect mirror symmetry that easily occurs in FCC Ag due to its low stacking fault energy (16 mJ/m 2 ) 35 and has been shown to promote its own strengthening effect in sputtered nanotwinned Ag metals 3,36-38 . Figure 2 shows that the intercalated nanocrystalline Ag/amorphous Ni material displays a record-breaking hardness of 2.6 GPa at indentation depths larger than 175 nm, exceeding hardness measurements on sputtered pure nanotwinned (111) Ag 36 and Cu-mixed nanotwinned Ag 3 films, which were previously established as the record for nanostructured Ag materials. This effect could be partially attributed to the smaller grains achieved in this work compared to previous studies. Nevertheless, we compared our results to the hardness of sputtered 50% nanocrystalline Ag – 50% nanocrystalline Ni nanolaminates that were synthesized in past studies. Figure 2(b) indicates that the film produced is significantly harder than the standard Ag/Ni nanolaminates at an equivalent Ag layer thickness of 24 nm. This finding suggests that the strengthening is strongly correlated with the presence of amorphous Ni nanolayers, as opposed to thicker crystalline Ni layers. Moreover, we conducted atomistic simulations to study how ultrathin amorphous Ni layers could influence the plastic deformation mechanisms during nanoindentation. Figure 2(c)-(d) finds no difference on the dislocation slip, grain boundary activity, and the contact pressure (Supplementary Figure S2) in nanocrystalline Ag with or without amorphous Ni nanolayers. Therefore, we conclude that the high hardness of intercalated nanocrystalline Ag must result from hardening mechanisms that are intrinsic to the amorphous Ni nanolayers. Uniaxial tensile properties of the intercalated nanocrystalline Ag material are presented in Figure 3. In Figure 3(a), this material is found to repeatably exhibit an ultimate tensile strength of 677 MPa with 6.67% tensile elongation before the break point. By comparison, in-situ consolidated bulk nanograined Ag ( d = 13.5 nm) by Sun and Shen 20 reached less than half of those property values in uniaxial tensile testing. Also, there are no published tensile data for sputtered nanocrystalline-nanotwinned Ag-0.63wt% Cu 3 , nanotwinned pure (111) Ag 36 or 50% nanocrystalline Ag – 50% nanocrystalline Ni nanolaminates 39 . However, we measured 10.7% tensile elongation and a maximum tensile strength of 135 MPa in a coarse-grained annealed Ag foil, which is 500% smaller than in the Ni-intercalated nanocrystalline Ag. The exceptional tensile behavior of intercalated nanocrystalline Ag is ascribed to more pronounced strain-hardening rates compared to consolidated nanoscale Ag and coarse-grained annealed Ag, as shown in Figure 3(b). The literature recognizes two major limitations to tensile ductility in nanocrystalline materials: defects from processing, such as voids or cracks, and force instability from strain-localized failure 40 . The absence of strain hardening (ds/de = 0) generally leads to localized deformation and low ductility 41 . However, post-mortem surface analysis in the inset of Figure 3(b) revealed no evidence of shear localization or grain growth across the multilayers during plastic deformation. Additionally, our synthesized film was defect-free. Therefore, we attribute the enhanced tensile ductility of intercalated nanocrystalline Ag to the retardation of force instabilities from these high strain hardening rates. Furthermore, we analyzed the chemical composition of the Ni nanolayers using HAADF-STEM. Figures 4(a1-a5) indicate uneven element mixing, where substantial quantities of Ag atoms have diffused into both thin and thick Ni nanolayers, while only negligible concentrations of Ni atoms have moved to the Ag layers. Moreover, concentrations of O and S atoms were detected, with a notable affinity observed for O to bind to Ni, as evidenced in Figure 4(a4). We hypothesize that any detected air contamination likely occurred during the STEM sample preparation process rather than during synthesis. This speculation is based on previous research findings 42,43 , which demonstrated that direct-current reactive magnetron sputtering of Ni films with oxygen resulted in the formation of crystalline NiO films, specifically bunsenite, as opposed to amorphous NiO, which contradicts our observations in STEM. The Ag concentration in Ni nanolayers varies between 5 at. % and 9 at. % (Figure 4(b1-b4), Supplementary Figure S6 and Tables S1-S2), therefore revealing that the nanocrystalline Ag layers are intercalated by amorphous Ni-Ag films. To better understand the relationship between amorphous Ni-Ag alloy nanolayers and strain hardening effects at atomic scale, we examined the mechanical behavior and underlying plasticity mechanisms through large-scale atomistic simulations (see Methods). The atomistic model, depicted in Figure 5(a), consisted of a periodic arrangement of two amorphous Ni-9Ag alloy nanofilms stacked between two nanocrystalline Ag layers. These layers had an average grain diameter of 21.7 nm and an intragranular twin thickness of 2.8 nm. Previous atomistic simulations of pure nanocrystalline-twinned Ag with similar microstructural characteristics mainly showed plastic softening through combined partial dislocation nucleation, detwinning and grain-boundary sliding mechanisms 3,44 . Additionally, two nanolayer thicknesses, h = 1.6 and 3.0 nm, have been considered to accurately match the experimental material. In Figure 5(b), the hybrid Monte-Carlo and molecular dynamics (MC/MD) simulation of thermal annealing at 450 K and cooling to 300 K under zero stress reveal that the equilibrium microstructure resulted in 0.012 % of Ni atoms segregated to the grain boundaries in the nanocrystalline Ag layers. Small amorphous Ni-rich clusters also formed inside the amorphous Ni-9Ag alloy films, as identified in the inset of Figure 5(b) using polyhedral template matching analysis. The formation of small Ni clusters is known to occur naturally in the amorphous structures of the immiscible Ag - Ni system at equilibrium 45 . The importance of strain-induced chemical short-range order (CSRO) on strain hardening is emphasized in the simulated stress – strain curves in Figure 5(c). To elucidate the influence of CSRO during deformation, we utilized two distinct approaches. First, we employed a classical MD approach, where compression of the simulation box occurred at a high strain rate (10 8 s -1 ), effectively blocking the presence of CSRO. Second, we utilized a hybrid MC/MD approach, allowing for CSRO to occur at 300 K while deforming the simulation box. The goal of our MC/MD approach is to continuously lower the energy of the amorphous structures during deformation, to reach both chemical and structural relaxation by forming more of the motifs with higher symmetry and lower energy states. We find that the simulated stresses are the lowest in pure nanocrystalline Ag, due to strain softening after plastic yielding and increase significantly with the addition of amorphous Ni-9Ag alloy nanolayers. Specifically, Figure 5(c) shows that the average flow strength (between 10% and 33% strain) is 14% higher in intercalated nanocrystalline Ag (1.37 GPa) than in pure nanocrystalline Ag (1.20 GPa) using the classical approach. Remarkably, however, the average flow strength increases by 27% with the intercalated nanocrystalline Ag (1.53 GPa) using the hybrid MC/MD approach. This type of hardening surpasses traditional theoretical predictions obtained with a linear rule of mixtures, which corresponds to a composite strength of 1.26 GPa with a volume fraction of amorphous Ni-9Ag material of 12% in our thick-layer model. Additionally, we observe that the simulated stress – strain curves remain independent of the amorphous nanolayer thickness, also disagreeing with the rule of mixtures. Figures 5(d) and 5(e) shows that the strain-hardening mechanism could relate to strong CSRO associated with the segregation of amorphous Ni clusters at the center of the amorphous Ni-Ag alloy nanolayers. As illustrated in Supplementary Figure S7, separate MD simulations revealed that strength of this amorphous Ni structure is significantly stronger than the amorphous Ni-Ag alloy, as it is subject to its own strain hardening mechanism through dynamic recrystallization. These predictions are consistent with the structural evolution depicted in Figure 5(e) revealing the formation of some crystalline Ni clusters inside the amorphous Ni-rich nanolayers at large strain. Moreover, our MC/MD simulation approach predicted that the Ni concentration inside the nanocrystalline Ag layers gradually increased up to 1.2 at.% Ni with the applied strain (Supplementary Figure S8), which agrees with our STEM observations of Ni mixing into the nanocrystalline Ag layers. However, previous hybrid MC/MD simulations on nanocrystalline Ag-Ni alloy polycrystals 33 suggest a less than 5% increase in strength induced by grain-boundary segregation of 1.2 at.% Ni atoms in nanocrystalline Ag (Supplementary Figure S9), posing a limitation on grain-boundary segregation hardening in the present study. Therefore, collectively, our simulations give credence for an intrinsic strain-hardening mechanism from intercalation of amorphous Ni-rich nanolayers that differs from classical dislocation-based strengthening mechanisms seen in conventional nanolayered 46 and nanocrystalline materials 41 . To substantiate the CSRO, we employed HAADF-STEM to re-examine the chemical distribution within amorphous Ni-Ag nanolayers of the plastically deformed intercalated nanocrystalline Ag material post-failure. Figure 6 illustrates instances of chemical clustering and short-range ordering observed within individual nanolayers. Heterogeneous distribution of Ag atoms within a nanolayer is evident from Figures 6(a)-(d), revealing Ag connections highlighted with yellow arrows between Ni-rich amorphous clusters. Each amorphous Ni cluster exhibits varying Ag composition, as demonstrated in Figure 6(e) and Supplementary Figures S10-S13, through brightness variations at different positions within the nanolayers. Furthermore, atomic-resolution STEM images in Figure 6(f) and Supplementary Figure S14 reveal the occurrence of short-range crystalline clusters (2-3 nm) within the amorphous nanolayers. It is worth noting that, although some crystalline clusters were also observed in the nanolayers of undeformed specimens, their number was noticeably higher in the deformed specimen. Moving forward, to isolate the hardening effect of strain-induced CSRO in amorphous Ni-rich nanolayers, we investigated the mechanical behaviour of a hypothetical amorphous structure made with 100% Ni-9Ag alloy by hybrid MC/MD simulation. Our findings, illustrated in Figure 7(a)-(c), indicate two regimes of strain-induced phase transformation. Initially, there is a short-range ordering phase, wherein small amorphous and pure Ni clusters evolve into larger ones with increasing applied strain, up to 20%. Subsequently, dynamic recrystallization of the larger Ni clusters occurs, followed by the formation of amorphous pure Ag clusters within the amorphous Ni-Ag clusters as the strain surpasses 20%. Quantitative analysis presented in Figure 7(d) emphasizes the predominance of short-range ordering effects in the amorphous Ni-9Ag material until dynamic recrystallization takes place. Interestingly, the simulated stress-strain curves depicted in Figure 7(e) highlight a strong correlation between strain hardening and the initial CSRO stage during hybrid MC/MD simulation. This stands in contrast to the lack of strain hardening observed in the amorphous plastic flow simulated in the Ni-9Ag alloy without CSRO using the classical approach. The CSRO-induced hardening behaviour is different from Ni crystallization-induced hardening predicted in Figure 7(e) and Supplementary Figure S7. In summary, our simulations provide direct evidence linking strain hardening behavior to strain-induced CSRO in the amorphous Ni-Ag nanolayers. Conclusion We have observed a nanoscale strengthening mechanism in both experiments and atomistic simulations in nanocrystalline Ag films by intercalation of ultrathin amorphous Ni-rich layers, which was found to fundamentally differ from grain-boundary and interface strengthening mechanisms seen in traditional nanolaminated metallic materials. The introduction of amorphous Ni-rich nanolayers simultaneously increased the grain stability, hardness, tensile yield strength, strain-hardening rates, and tensile ductility in nanocrystalline Ag, breaking record levels for this metal. The underlying strain-hardening mechanism was intrinsic to the amorphous Ni-rich nanolayer structure and resulted from chemical short-range ordering due to substantial quantities of Ag atoms mixed with the nanolayers at varying concentrations. This discovery is important for the development of tougher Ag film materials for deformable conductive electrodes with unprecedented mechanical and physical properties. Methods Materials synthesis. A film sample of nanocrystalline Ag/amorphous Ni multilayer was synthesized by magnetron sputtering 47 onto a oriented Si wafer. Three 50 mm diameter Ag targets were arranged in a confocal geometry to sputter onto a 152-mm diameter substrate, which was rotated at 15 revolutions per minute. The substrate was cooled by liquid N2. A fourth target of Ni metal, 76 mm in diameter, was also arranged in a confocal geometry outside the circle of Ag targets. For all sputtering runs, the base pressure was < 5 × 10 -8 torr and the working pressure was 5 mtorr of Ar. The three sputtering guns with Ag targets were operated together for 2 seconds at 175 W, while the sputtering gun with the Ni target was operated for 20 s at 175 W. The sputtering rates were estimated to be 11.8 nm/s and 0.127 nm/s for the Ag and Ni layers, respectively. The deposited multilayer was 3.2 μm in total thickness as verified by field-emission scanning electron microscopy (FESEM). Electron microscopy. Cross-sectional transmission electron microscope (TEM) samples were prepared by a focused ion beam instrument with a gas injection system (Helios, Thermo Fisher Scientific Ltd.). The TEM samples were then investigated by an aberration-corrected TEM (Titan Cube, Thermo Fisher Scientific Ltd.) at 200 kV. Energy-dispersive X-ray spectroscopy (EDS) studies were carried out with a Super-X EDX detector and GIF Quantum ER (965) system. Fracture surfaces after tensile testing were analysed by secondary electron imaging in a FESEM (Zeiss Sigma 300VP) operated at 5 kV. Nanoindentation testing. Nanoindentation experiments were carried out under displacement-control mode with a Hysitron Ti-750 nanomechanical testing system (Eden Prairie, MN, USA) at the Manitoba Institute for Materials (MIM). The nanoindenter used a Diamond Berkovich tip, which was repetitively loaded and then unloaded in 18 force increments up to a maximum force of 5 mN. The Oliver-Pharr method was used to extract the effective modulus and hardness. Indentations with different depths ranging from 100-300 nm were collected. We found that the hardness values were stabilized at an indentation depth of 175 nm into the film. Each indentation was performed using a rectangular pattern with a minimum distance of 10 microns between each other to prevent the interference of the stress field caused by nearby indentations. Tensile mechanical testing. The multilayered film was cut directly on the Si wafer into 25-mm-long strips using a 45-mm tungsten steel rotary blade (Olfa) and a flat metallic ruler (Westcott). This technique was found to significantly reduce surface defects introduced by other methods such as precision laser cutting. The width was 2.7 ± 0.01 mm as measured with an optical microscope at 100X magnification. The film strip was gently detached from the wafer using flat-ended tweezers. Square pieces of one-sided Cu tape were sticked at each end of the strip and carefully lifted to a mini-tensile testing machine with a 500 N load cell (Kammrath and Weiss). The strain rate was 10 -4 s -1 . Testing was repeated three times to verify the reproducibility of the results. For comparison, the tensile behaviour of an annealed pure Ag foil of 50 microns in thickness (GoodFellow) was characterized using the same methodology. Strain hardening rates were calculated as a function of strain by fitting the stress-strain curve with a fourth-order polynomial function for strains between 0.01 and the maximum strain at failure and deriving this function. MD simulation. MD simulations were performed using the Large-Scale Atomic/Molecular Massively Parallel Simulator (LAMMPS) 48 with a semi-empirical Finnis-Sinclair interatomic potential for Ag-Ni alloys developed by Pan et al. 31 . This potential was fitted on ab initio calculations to accurately predict the stacking-fault energy curve, grain boundary energies and interface segregation energies of Ni atoms in FCC Ag. Atomistic models were generated using the Atomsk software 49 . The simulation box was 52 nm × 52 nm × 52 nm. A set number of FCC Ag grains were placed with random distribution and random orientation by a Voronoi Tessellation algorithm. Perfectly coherent nanotwins were introduced with a constant twin boundary spacing of 2.8 nm. Other models were also created without nanotwins for comparison. Each boundary was defined as periodic. The final grain diameter after relaxation was quantified using the grain analysis in the atomic visualization software OVITO 50 . To create amorphous Ni-9Ag alloy layers, Ag atoms were removed in layers and replaced with crystalline FCC Ni atoms to obtain an estimate of the total Ni atoms required for the amorphous layer. After relaxation, the crystalline Ni layer compressed by ~1 nm. Accounting for this effect, the defined region to remove Ag atoms was increased to achieve the desired thickness as seen in the experiment. The model was then generated again by inserting 91% Ni and 9% Ag atoms in a random fashion to generate an amorphous layer. Each Ag/Ni model contained 8.13 million atoms and the pure nc-Ag models contained 7.81 million atoms. Each model was first relaxed under isobaric-isothermal ensemble (NPT) at zero pressure and a temperature of 450 K for 100 ps, cooled to 300 K over 50 ps and then maintained at 300 K for another 50 ps. The time step was 5 fs. Subsequently, the model was deformed under compression by applying a constant engineering strain rate to the simulation box of 0.0001 ps -1 in the negative z direction. For the classical simulation approach, deformation was performed under an NPT ensemble at 300 K with zero pressure in the x and y axes. To study CSRO with the hybrid MC/MD approach, we modified the variance-constrained semi-grand canonical ensemble algorithm described in Reference 32 by introducing deformation of the simulation box at constant strain rate and constant temperature (300 K). The atomic structure and short-range order were studied using the common-neighbor analysis and the polyhedral template matching analysis, respectively, in OVITO. Declarations Acknowledgment: RP and FS received support by the U.S. Department of Energy (DOE) under grant no. DE-SC0020054 and used computational resources from the Extreme Science and Engineering Discovery Environment (XSEDE) supported by the National Science Foundation (NSF) under grant no. ACI-1548562 and the National Energy Research Scientific Computing Center (NERSC), a U.S. DOE Office of Science User Facility operated under contract no. DE-AC02-05CH11231. RTO and LZ acknowledge support from Laboratory Directed Research and Development at Ames National Laboratory, operated for the U.S. DOE by Iowa State University of Science and Technology under contract No. DE-AC02-07CH11358. YL and GZZ acknowledge support from the Natural Sciences and Engineering Research Council of Canada (NSERC). CD received support from the NSERC Discovery grant no. RGPIN-2019-05834. The field-emission SEM used in this study was acquired through NSF MRI grant no. 1828371. Author Contributions: FS and RO conceived the original hypothesis and managed the overall project. JO, LZ and RO produced the sputter deposited film and TEM/STEM images. YL, GZZ and CD conducted the nanoindentation experiments. FS conducted the tensile testing and FESEM. RP and FS performed and analyzed the atomistic simulations and wrote the manuscript. All authors have contributed to the results discussion and given approval to the final version of the manuscript. References Z. Cheng, L. L., S. Xu, M. Lu and X. Wang. Temperature Dependence of Electrical and Thermal Conduction in Single Silver Nanowire. Scientific Reports 5 (2015). Kemp, W. R. G., Klemens, P. G., Sreedhar, A. K., White, G. K. & Simon, F. E. The thermal and electrical conductivity of silver-palladium and silver-cadmium alloys at low temperatures. 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Development of a Semi-empirical Potential for Simulation of Ni solute Segregation into Grain Boundaries in Ag. Modelling and Simulation in Materials Science and Engineering 26 , 075004 (2018). Pan, Z. & Sansoz, F. Heterogeneous solute segregation suppresses strain localization in nanocrystalline Ag-Ni alloys. Acta Materialia 200 , 91-100 (2020). https://doi.org:https://doi.org/10.1016/j.actamat.2020.08.074 Picard, E.-A. & Sansoz, F. Ni solute segregation and associated plastic deformation mechanisms into random FCC Ag, BCC Nb and HCP Zr polycrystals. Acta Materialia 240 , 118367 (2022). https://doi.org:https://doi.org/10.1016/j.actamat.2022.118367 Baras, F., Politano, O., Li, Y. & Turlo, V. A Molecular Dynamics Study of Ag-Ni Nanometric Multilayers: Thermal Behavior and Stability. Nanomaterials 13 , 2134 (2023). Anderson, P. M., Hirth, J. P. & Lothe, J. Theory of Dislocations . third edn, (Cambridge University Press, 2017). D. Bufford, H. W. a. X. Z. High strength, epitaxial nanotwinned Ag films. Acta Materialia 59 , 93-101 (2011). D. Bufford, H. W. a. X. Z. Thermal Stability of twins and strengthening mechanisms in differently ooriented epitaxial nanotwinned Ag films. Journal of Materials Research 28 , 1729-1739 (2013). Hodge, T. A. F. a. A. M. On the mechanical performance and deformation of nanotwinned Ag. APL Mater 2 (2014). Kang, B. C., Kim, H. Y., Kwon, O. Y. & Hong, S. H. Bilayer thickness effects on nanoindentation behavior of Ag/Ni multilayers. Scripta Materialia 57 , 703-706 (2007). https://doi.org:https://doi.org/10.1016/j.scriptamat.2007.06.038 Koch, C. C. Optimization of strength and ductility in nanocrystalline and ultrafine grained metals. Scripta Materialia 49 , 657-662 (2003). https://doi.org:https://doi.org/10.1016/S1359-6462(03)00394-4 Meyers, M. A., Mishra, A. & Benson, D. J. Mechanical properties of nanocrystalline materials. 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Mechanical Properties of Metal Nanolaminates. Annual Review of Materials Research 52 , 281-304 (2022). https://doi.org:https://doi.org/10.1146/annurev-matsci-081320-031236 Sigmund, P. Theory of Sputtering. I. SPuttering Yield of Amorphous and Polycrystalline Targets. Physical Review 184 , 383-416 (1969). Plimpton, S. Fast Parallel Algorithms for Short-Range Molecular Dynamics. J. Comp. Phys. 117 (1995). Hirel, P. Atomsk: A tool for manipulating and converiting atomic data files. Phys. Comm. 197 (2015). Stukowski, A. Visualization and analysis of atomistic simulation data with OVITO - the Open Visualization Tool Modelling Simul. Mater. Sci. Eng. 18 (2010). Additional Declarations There is NO Competing Interest. Supplementary Files SupplementaryInformationSubmittedversion.pdf Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-4402670","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":307942841,"identity":"8c8cb4f4-e6ec-4a9e-b5e1-c2385cc5e9c9","order_by":0,"name":"Frederic Sansoz","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA8ElEQVRIiWNgGAWjYBAC9gYGBgkwggI5CMWGWwvPATQtxsRqQYDEBoJapA8fvPFxj4U8A//hZw9/VNSlb7iRncDwoewwbi18acmWM55JGDZIpJkb85xhy91wI3cD44xzuLXY8/CYSfMckEgAOs9MmrGNJ3fDmbMbmHnb8NjCw/9N+g9IC//xb5I/2yTSDUBa/uLVwsMmzQDSwpBjJsHbZpBgcLx3AzMjXi1sxpY9ByQM2yRyyqR5ziQYzgRqOdhzLh2PFuaHN34cqJPn5z++TRIYYvJ8h3k3PvhRZo1TCxygRMQBwupHwSgYBaNgFOADACegTc/0jmkOAAAAAElFTkSuQmCC","orcid":"https://orcid.org/0000-0002-2782-1832","institution":"University of Vermont","correspondingAuthor":true,"submittingAuthor":false,"prefix":"","firstName":"Frederic","middleName":"","lastName":"Sansoz","suffix":""},{"id":307942842,"identity":"7f309c05-8313-4999-8676-ea975b3457a4","order_by":1,"name":"Malcolm Pringle","email":"","orcid":"https://orcid.org/0009-0000-9168-4599","institution":"University of Vermont","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Malcolm","middleName":"","lastName":"Pringle","suffix":""},{"id":307942843,"identity":"141e5250-deca-40bd-8c08-1cce7b1467e5","order_by":2,"name":"Jin-Su Oh","email":"","orcid":"https://orcid.org/0000-0002-7462-3142","institution":"Ames National Laboratory","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Jin-Su","middleName":"","lastName":"Oh","suffix":""},{"id":307942844,"identity":"d2ba2154-258e-4f86-8a6a-33467135a390","order_by":3,"name":"Lin Zhou","email":"","orcid":"https://orcid.org/0000-0003-2286-6510","institution":"Ames National Laboratory","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Lin","middleName":"","lastName":"Zhou","suffix":""},{"id":307942845,"identity":"2ba986a6-0877-42b5-b9fc-964588f93007","order_by":4,"name":"Ryan Ott","email":"","orcid":"","institution":"Ames Laboratory","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Ryan","middleName":"","lastName":"Ott","suffix":""},{"id":307942846,"identity":"d3410f04-4eda-4799-a275-ad12b2436e7d","order_by":5,"name":"Yushun Liu","email":"","orcid":"","institution":"University of Manitoba","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Yushun","middleName":"","lastName":"Liu","suffix":""},{"id":307942847,"identity":"b395e9cd-5f5d-46df-bdb4-0dfccae7cfc7","order_by":6,"name":"Guozhen Zhu","email":"","orcid":"","institution":"University of Manitoba","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Guozhen","middleName":"","lastName":"Zhu","suffix":""},{"id":307942848,"identity":"e5758070-0546-4ce8-975a-af0736795dad","order_by":7,"name":"Chuang Deng","email":"","orcid":"https://orcid.org/0000-0002-4604-1217","institution":"University of Manitoba","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Chuang","middleName":"","lastName":"Deng","suffix":""}],"badges":[],"createdAt":"2024-05-10 21:43:03","currentVersionCode":1,"declarations":{"humanSubjects":false,"vertebrateSubjects":false,"conflictsOfInterestStatement":false,"humanSubjectEthicalGuidelines":false,"humanSubjectConsent":false,"humanSubjectClinicalTrial":false,"humanSubjectCaseReport":false,"vertebrateSubjectEthicalGuidelines":false,"coiExplicitlySet":false},"doi":"10.21203/rs.3.rs-4402670/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-4402670/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":57407065,"identity":"2fd001fa-5959-43a0-9ece-71af1ee7e198","added_by":"auto","created_at":"2024-05-30 09:33:42","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":377139,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eMicrostructure of sputtered nanocrystalline Ag intercalated with ultrathin amorphous Ni layers. \u003c/strong\u003e(a) Cross-section TEM image and (b) associated electron diffraction. (c) No electron intensity peaks are found for the interplanar planar spacings of crystalline Ni (highlighted in red), which is evidence that the Ni nanolayers are amorphous. (d)-(f) High-resolution HAADF and bright-field (BF) STEM images.\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-4402670/v1/c9940f098619acc1f15396aa.png"},{"id":57408020,"identity":"8b2f7035-26e1-4f9f-a2ec-59b964297f79","added_by":"auto","created_at":"2024-05-30 09:49:43","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":362520,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eHardness properties of sputtered nanocrystalline Ag intercalated with amorphous Ni nanolayers. \u003c/strong\u003e(a)\u003cstrong\u003e \u003c/strong\u003eNanoindentation hardness as a function of contact depth. Literature data obtained for sputtered nanocrystalline-nanotwinned Ag-0.63wt% Cu (Ke et al.\u003csup\u003e3\u003c/sup\u003e) and sputtered nanotwinned pure (111) Ag (Bufford et al.\u003csup\u003e36\u003c/sup\u003e) are shown for reference. (b) Comparison of average hardness measured on the material in this work against the available data for sputtered 50% nanocrystalline Ag – 50% nanocrystalline Ni nanolaminates (Kang et al.\u003csup\u003e39\u003c/sup\u003e).\u0026nbsp;\u0026nbsp; For the same Ag layer thickness, adding amorphous Ni nanolayers produces a record-breaking hardness exceeding that of traditional nanolaminated films. Molecular dynamics simulation snapshots of the von-Mises shear strain distribution under nanoindentation in pure nanocrystalline Ag containing (c) no Ni layer, (d) a single Ni nanolayer distanced at 24 nm from the surface, and (e) a single Ni nanolayer distanced at 12 nm from the surface. Slip transmission across grains in nanocrystalline Ag subjected to tip indentation is unaffected by the amorphous Ni nanolayers.\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-4402670/v1/d76fce77af4b4880b0789607.png"},{"id":57407069,"identity":"7a57a5ba-acdd-4a99-b65e-71cd2bae0657","added_by":"auto","created_at":"2024-05-30 09:33:43","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":169332,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eUniaxial\u003c/strong\u003e \u003cstrong\u003etensile properties of a 3-micron-thick sputtered nanocrystalline Ag intercalated with amorphous Ni nanolayers,\u003c/strong\u003e \u003cstrong\u003ein-situ consolidated bulk nanocrystalline Ag (Sun and Chen\u003c/strong\u003e\u003csup\u003e\u003cstrong\u003e20\u003c/strong\u003e\u003c/sup\u003e\u003cstrong\u003e) and a coarse-grained annealed Ag foil. \u003c/strong\u003e(a)\u003cstrong\u003e \u003c/strong\u003eStress-strain diagrams. The superimposed bold line in black corresponds to the polynomial fitting used to obtain strain hardening rates. A substantial gain in both yield strength and tensile ductility is found in the presence of amorphous Ni nanolayers. The inset image shows the tensile foil specimen fabricated in this study. (b) Strain hardening rates. The inset in (b) shows the fracture surface of the intercalated nanocrystalline Ag film after failure. It indicates that grain growth remained limited up to the break point.\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-4402670/v1/d56d0e6190852482bae1d411.png"},{"id":57408022,"identity":"2dac04b2-b1fb-44ef-9d76-2a89dee242f5","added_by":"auto","created_at":"2024-05-30 09:49:43","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":1041946,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eChemical analysis by HAADF-STEM and EDS mapping across (a1)-(a5) five Ag/Ni layers and (b1)-(b2) a single amorphous Ni nanolayer.\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-4402670/v1/05a7443f3791446c2688ab72.png"},{"id":57407658,"identity":"5b2fa31d-3b7f-4f66-8da1-9d3ad6087529","added_by":"auto","created_at":"2024-05-30 09:41:43","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":731238,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eHybrid Monte-Carlo and molecular dynamics (MC/MD) simulations of chemical short-range order (CSRO) and mechanical behaviour in amorphous Ni-Ag alloy-intercalated nanocrystalline Ag under compression along the z-axis normal to the layers. \u003c/strong\u003e(a) Microstructure of the undeformed atomistic model with thick amorphous Ni-Ag nanolayers (\u003cem\u003eh\u003c/em\u003e = 3.0 nm) by common-neighbor analysis. (b). Identification of local amorphous and crystalline structures by polyhedral template matching analysis. All atoms identified as pure crystalline Ag have been removed for clarity. (c) Simulated true stress – true strain curves by classical MD with limited CSRO and hybrid MC/MD with strong CSRO permitted. Two nanolayer thicknesses have been considered, \u003cem\u003eh\u003c/em\u003e = 1.6 and 3.0 nm. (d) - (e) Snapshots of the classical MD and hybrid MC/MD simulations after 18% deformation in the model with thick amorphous Ni-Ag nanolayers. Strain-induced CSRO is pronounced in the amorphous nanolayers by hybrid MC/MD.\u003c/p\u003e","description":"","filename":"5.png","url":"https://assets-eu.researchsquare.com/files/rs-4402670/v1/ecc684192e90251215e2a58a.png"},{"id":57407654,"identity":"bce7fa83-b229-4296-98dc-18c25cbdb865","added_by":"auto","created_at":"2024-05-30 09:41:43","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":591007,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eDirect STEM evidence of short-range order within the amorphous Ni-Ag alloy nanolayers after 6.7% tensile deformation.\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"6.png","url":"https://assets-eu.researchsquare.com/files/rs-4402670/v1/35fcd7fdeae8a8a6e1e43cee.png"},{"id":57407066,"identity":"0f9b9405-f0a8-4f00-9e34-4347dbc24005","added_by":"auto","created_at":"2024-05-30 09:33:43","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":298799,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eHybrid MC/MD simulations of short-range order hardening in a fully amorphous Ni-9Ag alloy material deformed by compression.\u003c/strong\u003e \u0026nbsp;(a)-(c) Atomistic snapshots of the local structure identified by polyhedral template matching analysis at different applied strains. (d) Phase change as a function of applied strain. (e) Simulated true stress – true strain curves by either classical MD with no CSRO or hybrid MC/MD with strong CSRO. Short-range order hardening is evidenced from yielding up to 20% strain, followed by single phase Ni crystallization beyond 20%.\u003c/p\u003e","description":"","filename":"7.png","url":"https://assets-eu.researchsquare.com/files/rs-4402670/v1/5a98b8fcd7c6c2d3bb03c22b.png"},{"id":60921373,"identity":"d9458e47-cd93-4363-9e05-e3ed8bc96058","added_by":"auto","created_at":"2024-07-23 14:53:23","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":4265421,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-4402670/v1/cc193001-f20a-40df-836f-a2f8fb61fecf.pdf"},{"id":57408540,"identity":"8bc33b0c-8f97-4aa0-b3c6-b7a294c32e16","added_by":"auto","created_at":"2024-05-30 09:57:43","extension":"pdf","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":4522240,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cbr\u003e\u003c/p\u003e","description":"","filename":"SupplementaryInformationSubmittedversion.pdf","url":"https://assets-eu.researchsquare.com/files/rs-4402670/v1/71403489ca6c7c95a1d8e63c.pdf"}],"financialInterests":"There is \u003cb\u003eNO\u003c/b\u003e Competing Interest.","formattedTitle":"Short-Range Order Enhances Strength and Tensile Ductility in Nanocrystalline Silver with Intercalation of Amorphous Nickel Nanolayers","fulltext":[{"header":"Introduction","content":"\u003cp\u003eRegarding its high electrical conductivity\u003csup\u003e1\u003c/sup\u003e, Ag is a reference metal against which other materials are generally tested. Utilizing pure Ag over Ag alloys has clear advantages for improving thermal and electrical performances\u003csup\u003e2,3\u003c/sup\u003e and is of practical importance for conductive film electrodes in flexible devices\u003csup\u003e4-7\u003c/sup\u003e. Despite this quality, the low strength and extreme softness of a pure Ag metal imposes significant limitations for deformable films and coatings. Two common methods for enhancing strength and hardness in pure metal films are nanoscale grain refinement and nanolayer structuring. Yet these methods present unresolved challenges when applied to pure Ag films.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThe first approach for strengthening crystalline films is to reduce the average grain diameter to leverage grain-boundary effects associated with Hall-Petch hardening mechanisms\u003csup\u003e8-10\u003c/sup\u003e. Regardless of its potential benefits, this approach leads to a severe loss of strain hardening and tensile elongation\u003csup\u003e11,12\u003c/sup\u003e, due to strain localization and cracking mechanisms at the interfaces\u003csup\u003e13-16\u003c/sup\u003e. Furthermore, there is a maximum strength limit at which nanocrystalline materials become softer as the grain size decreases at the nanoscale, known as Hall-Petch breakdown, caused by intergranular plastic deformation from the high grain-boundary density\u003csup\u003e17,18\u003c/sup\u003e. Previous atomistic simulations have suggested that the optimal grain size for maximum hardness in pure Ag is in the 16-20 nm range\u003csup\u003e19\u003c/sup\u003e, but achieving this size experimentally is difficult due to the high instability of pure nanosized Ag grains\u003csup\u003e20\u003c/sup\u003e. The smallest stable grain size of pure face-centered cubic (FCC) Ag made by magnetron sputtering was 150 nm\u003csup\u003e21\u003c/sup\u003e. To stabilize the grain size and twin spacing in FCC Ag, adding small concentrations of solute atoms to the grain boundaries can be effective; for example, nanocrystalline Ag films doped with trace amounts of Cu have a stable grain size down to 50 nm\u003csup\u003e3\u003c/sup\u003e. Introducing higher solute concentrations can negatively impact the high thermal and electrical conductivity of Ag crystals\u003csup\u003e22\u003c/sup\u003e. However, conductivity remains high when adding high amounts of Cu in multilayered Ag/Cu materials\u003csup\u003e23\u003c/sup\u003e.\u003c/p\u003e\n\u003cp\u003eThe second strengthening approach is by deposition of alternating nanoscale crystalline-amorphous layers of variable thickness\u003csup\u003e24-26\u003c/sup\u003e. Crystalline nanolayers have unique strain hardening mechanisms due to the amount of stress required to move lattice dislocations across parallel interfaces\u003csup\u003e27,28\u003c/sup\u003e. Additionally, crystalline-amorphous nanolaminates are strengthened by the special interface structure between crystalline and amorphous layers and the obstacle formed by the amorphous layers to the propagation of slip bands\u003csup\u003e24\u003c/sup\u003e. All evidence proves that prolonging the tensile ductility under plastic deformation requires materials to exhibit more strain hardening. However, strain-hardening was absent in nanolayered crystalline-amorphous Cu-Zr films\u003csup\u003e24,25,29\u003c/sup\u003e, because incorporating non-crystalline layers to crystalline films gave rise to a transition from hardening to softening behavior\u003csup\u003e25\u003c/sup\u003e and brittle cracking\u003csup\u003e29\u003c/sup\u003e.\u003c/p\u003e\n\u003cp\u003eIn this article, we report experiments and atomistic simulations on nanocrystalline Ag films with maximum hardness and strain hardening characteristics obtained by intercalating nanoscale amorphous Ni-rich layers at a crystalline-to-amorphous thickness ratio of 0.1. The choice for ultrathin amorphous Ni layers is important in several aspects. First, past experimental studies\u003csup\u003e24,30\u003c/sup\u003e have shown that reducing the thickness of amorphous layers to a few nanometers is beneficial for reclaiming some tensile plastic elongation in nanolaminates, because thinner layers can serve as both sink and source for lattice dislocations similarly to grain boundaries. In fact, an experimental study on nanocrystalline Ag/amorphous Cu-Zr nanolaminates found that the critical strain before fracture could be maximized at a thickness ratio of 0.1, although the underlying deformation mechanism was dominated by cracking of the amorphous Cu-Zr layers\u003csup\u003e29,30\u003c/sup\u003e. Second, Ag and Ni are immiscible, resulting in heterogeneous Ni phase separation and clustering at interfaces in nanocrystalline FCC Ag, which helps with the stability of ultrathin Ni layers\u003csup\u003e31-34\u003c/sup\u003e and \u0026nbsp;should yield intriguing deformation mechanisms that have not been fully explored so far.\u0026nbsp;Third, the defined thickness between amorphous nanolayers can control the grain size, thereby providing a viable solution for stabilizing nanograins in pure Ag at the maximum Hall-Petch strength limit\u003csup\u003e19\u003c/sup\u003e.\u003c/p\u003e"},{"header":"Results and Discussion","content":"\u003cp\u003eWe synthesized a nanocrystalline Ag foil intercalated with ultrathin Ni layers by magnetron sputtering (see Methods). The foil was 3.2 mm in total thickness and composed of alternating pure nanocrystalline Ag and thin Ni layers of 23.6 \u0026plusmn; 0.5 nm and 2.5 \u0026plusmn; 0.3 nm in thickness, respectively, as shown by transmission electron microscopy (TEM) in Figure 1(a). Although the thickness was found to be uniform within one nanolayer, some Ni nanolayers could be found to be 1-2 nm thicker than others (Supplementary Figure S1). The Ni nanolayer structure was amorphous, as evidenced by the absence of crystal Ni peaks in the electron diffraction in Figures 1(b)-(c)\u0026nbsp;and the atomic-scale high-angle angular dark-field (HAADF) scanning transmission electron microscopy (STEM) in Figures 1(d)-(f). Each Ag layer was made of equiaxed grains with an average diameter of ~22 nm indicating that the grain size of these films depends on the Ag layer thickness,\u0026nbsp;which is consistent with similarly synthesized nanolaminates in the literature.\u0026nbsp;This corresponds to the smallest grain size ever recorded for sputtered pure Ag materials, suggesting that the intercalation of amorphous Ni nanolayers between nanocrystalline Ag films improved microstructure stability during sputtering deposition. Further evidence for the exceptional grain stability of intercalated nanocrystalline Ag layers during plastic deformation experiments is presented below. Furthermore,\u0026nbsp;the material contained some intragranular nanoscale twins (Supplementary Figure S1). A twin boundary is a coherent crystalline interface with perfect mirror symmetry that easily occurs in FCC Ag due to its low stacking fault energy (16 mJ/m\u003csup\u003e2\u003c/sup\u003e)\u003csup\u003e35\u003c/sup\u003e and has been shown to promote its own strengthening effect in sputtered nanotwinned Ag metals\u003csup\u003e3,36-38\u003c/sup\u003e.\u003c/p\u003e\n\u003cp\u003eFigure 2 shows that the intercalated nanocrystalline Ag/amorphous Ni material displays a record-breaking hardness of 2.6 GPa at indentation depths larger than 175 nm, exceeding hardness measurements on sputtered pure nanotwinned (111) Ag\u003csup\u003e36\u003c/sup\u003e and Cu-mixed nanotwinned Ag\u003csup\u003e3\u003c/sup\u003e films, which were previously established as the record for nanostructured Ag materials. This effect could be partially attributed to the smaller grains achieved in this work compared to previous studies. Nevertheless, we compared our results to the hardness of sputtered 50% nanocrystalline Ag \u0026ndash; 50% nanocrystalline Ni nanolaminates that were synthesized in past studies. Figure 2(b) indicates that the film produced is significantly harder than the standard Ag/Ni nanolaminates at an equivalent Ag layer thickness of 24 nm. This finding suggests that the strengthening is strongly correlated with the presence of amorphous Ni nanolayers, as opposed to thicker crystalline Ni layers. Moreover, we conducted atomistic simulations to study how ultrathin amorphous Ni layers could influence the plastic deformation mechanisms during nanoindentation. Figure 2(c)-(d) finds no difference on the dislocation slip, grain boundary activity, and the contact pressure (Supplementary Figure S2) in nanocrystalline Ag with or without amorphous Ni nanolayers. Therefore, we conclude that the high hardness of intercalated nanocrystalline Ag must result from hardening mechanisms that are intrinsic to the amorphous Ni nanolayers.\u003c/p\u003e\n\u003cp\u003eUniaxial tensile properties of the intercalated nanocrystalline Ag material are presented in\u0026nbsp;Figure 3. In\u0026nbsp;Figure 3(a), this material is found to repeatably exhibit an ultimate tensile strength of 677 MPa with 6.67% tensile elongation before the break point. By comparison, in-situ consolidated bulk nanograined Ag (\u003cem\u003ed\u003c/em\u003e = 13.5 nm) by Sun and Shen\u003csup\u003e20\u003c/sup\u003e reached less than half of those property values in uniaxial tensile testing. Also, there are no published tensile data for sputtered nanocrystalline-nanotwinned Ag-0.63wt% Cu\u003csup\u003e3\u003c/sup\u003e, nanotwinned pure (111) Ag\u003csup\u003e36\u003c/sup\u003e or \u0026nbsp;50% nanocrystalline Ag \u0026ndash; 50% nanocrystalline Ni nanolaminates\u003csup\u003e39\u003c/sup\u003e. However, we measured 10.7% tensile elongation and a maximum tensile strength of 135 MPa in a coarse-grained annealed Ag foil, which is 500% smaller than in the Ni-intercalated nanocrystalline Ag.\u003c/p\u003e\n\u003cp\u003eThe exceptional tensile behavior of intercalated nanocrystalline Ag is ascribed to more pronounced strain-hardening rates compared to consolidated nanoscale Ag and coarse-grained annealed Ag, as shown in\u0026nbsp;Figure 3(b). The literature\u0026nbsp;recognizes two major limitations to tensile ductility in nanocrystalline materials: defects from processing, such as voids or cracks, and force instability from strain-localized failure\u003csup\u003e40\u003c/sup\u003e. The absence of strain hardening (ds/de\u0026nbsp;= 0) generally leads to localized deformation and low ductility\u003csup\u003e41\u003c/sup\u003e. However,\u0026nbsp;post-mortem surface analysis in the inset of\u0026nbsp;Figure 3(b)\u0026nbsp;revealed no evidence of shear localization or grain growth across the multilayers during plastic deformation.\u0026nbsp;Additionally, our synthesized film was defect-free. Therefore, we attribute the enhanced tensile ductility of intercalated nanocrystalline Ag to the retardation of force instabilities from these high strain hardening rates.\u003c/p\u003e\n\u003cp\u003eFurthermore, we analyzed the chemical composition of the Ni nanolayers using HAADF-STEM.\u0026nbsp;Figures 4(a1-a5)\u0026nbsp;indicate uneven element mixing, where substantial quantities of Ag atoms have diffused into both thin and thick Ni nanolayers, while only negligible concentrations of Ni atoms have moved to the Ag layers. Moreover, concentrations of O and S atoms were detected, with a notable affinity observed for O to bind to Ni, as evidenced in\u0026nbsp;Figure 4(a4). We hypothesize that any detected air contamination likely occurred during the STEM sample preparation process rather than during synthesis. This speculation is based on previous research findings\u003csup\u003e42,43\u003c/sup\u003e, which demonstrated that direct-current reactive magnetron sputtering of Ni films with oxygen resulted in the formation of crystalline NiO films, specifically bunsenite, as opposed to amorphous NiO, which contradicts our observations in STEM. The Ag concentration in Ni nanolayers varies between 5 at. % and 9 at. % (Figure 4(b1-b4), Supplementary Figure S6 and Tables S1-S2), therefore revealing that the nanocrystalline Ag layers are intercalated by amorphous Ni-Ag films.\u003c/p\u003e\n\u003cp\u003eTo better understand the relationship between amorphous Ni-Ag alloy nanolayers and strain hardening effects at atomic scale, we examined the mechanical behavior and underlying plasticity mechanisms through large-scale atomistic simulations (see Methods). The atomistic model, depicted in Figure 5(a),\u0026nbsp;consisted of a periodic arrangement of two amorphous Ni-9Ag alloy nanofilms stacked between two nanocrystalline Ag layers. These layers had an average grain diameter of 21.7 nm and an intragranular twin thickness of 2.8 nm. Previous atomistic simulations of pure nanocrystalline-twinned Ag with similar microstructural characteristics mainly showed plastic softening through combined partial dislocation nucleation, detwinning and grain-boundary sliding mechanisms\u003csup\u003e3,44\u003c/sup\u003e. Additionally, two nanolayer thicknesses, \u003cem\u003eh\u003c/em\u003e = 1.6 and 3.0 nm, have been considered to accurately match the experimental material. In Figure 5(b), the hybrid Monte-Carlo and molecular dynamics (MC/MD) simulation of thermal annealing at 450 K and cooling to 300 K under zero stress reveal that the equilibrium microstructure resulted in 0.012 % of Ni atoms segregated to the grain boundaries in the nanocrystalline Ag layers. Small amorphous Ni-rich clusters also formed inside the amorphous Ni-9Ag alloy films, as identified in the inset of Figure 5(b)\u0026nbsp;using polyhedral template matching analysis. The formation of small Ni clusters is known to occur naturally in the amorphous structures of the immiscible Ag - Ni system at equilibrium\u003csup\u003e45\u003c/sup\u003e.\u003c/p\u003e\n\u003cp\u003eThe importance of strain-induced chemical short-range order (CSRO) on strain hardening is emphasized in the simulated stress \u0026ndash; strain curves in Figure 5(c). To elucidate the influence of CSRO during deformation, we utilized two distinct approaches. First, we employed a classical MD approach, where compression of the simulation box occurred at a high strain rate (10\u003csup\u003e8\u003c/sup\u003e s\u003csup\u003e-1\u003c/sup\u003e), effectively blocking the presence of CSRO. Second, we utilized a hybrid MC/MD approach, allowing for CSRO to occur at 300 K while deforming the simulation box. \u0026nbsp;The goal of our MC/MD approach is to continuously lower the energy of the amorphous structures during deformation, to reach both chemical and structural relaxation by forming more of the motifs with higher symmetry and lower energy states.\u003c/p\u003e\n\u003cp\u003eWe find that\u0026nbsp;the simulated stresses are the lowest in pure nanocrystalline Ag, due to strain softening after plastic yielding and increase significantly with the addition of amorphous Ni-9Ag alloy nanolayers. Specifically, Figure 5(c) shows that the average flow strength (between 10% and 33% strain) is 14% higher in intercalated nanocrystalline Ag (1.37 GPa) than in pure nanocrystalline Ag (1.20 GPa) using the classical approach. Remarkably, however, the average flow strength increases by 27% with the intercalated nanocrystalline Ag (1.53 GPa) using the hybrid MC/MD approach. This type of hardening surpasses traditional theoretical predictions obtained with a linear rule of mixtures, which corresponds to a composite strength of 1.26 GPa with a volume fraction of amorphous Ni-9Ag material of 12% in our thick-layer model. Additionally, we observe that the simulated stress \u0026ndash; strain curves remain independent of the amorphous nanolayer thickness, also disagreeing with the rule of mixtures.\u003c/p\u003e\n\u003cp\u003eFigures 5(d) and 5(e)\u0026nbsp;shows that the strain-hardening mechanism could relate to strong CSRO associated with the segregation of amorphous Ni clusters at the center of the amorphous Ni-Ag alloy nanolayers. As illustrated in Supplementary Figure S7,\u0026nbsp;separate MD simulations revealed that strength of this amorphous Ni structure is significantly stronger than the amorphous Ni-Ag alloy, as it is subject to its own strain hardening mechanism through dynamic recrystallization. These predictions are consistent with the structural evolution depicted in Figure 5(e) revealing the formation of some crystalline Ni clusters inside the amorphous Ni-rich nanolayers at large strain.\u003c/p\u003e\n\u003cp\u003eMoreover, our MC/MD simulation approach predicted that the Ni concentration inside the nanocrystalline Ag layers gradually increased up to 1.2 at.% Ni with the applied strain (Supplementary Figure S8), which agrees with our STEM observations of Ni mixing into the nanocrystalline Ag layers. However, previous hybrid MC/MD simulations on nanocrystalline Ag-Ni alloy polycrystals\u003csup\u003e33\u003c/sup\u003e suggest a less than 5% increase in strength induced by grain-boundary segregation of 1.2 at.% Ni atoms in nanocrystalline Ag (Supplementary Figure S9), posing a limitation on grain-boundary segregation hardening in the present study. Therefore, collectively, our simulations give credence for an intrinsic strain-hardening mechanism from intercalation of amorphous Ni-rich nanolayers that differs from classical dislocation-based strengthening mechanisms seen in conventional nanolayered\u003csup\u003e46\u003c/sup\u003e and nanocrystalline materials\u003csup\u003e41\u003c/sup\u003e.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eTo substantiate the CSRO, we employed HAADF-STEM to re-examine the chemical distribution within amorphous Ni-Ag nanolayers of the plastically deformed intercalated nanocrystalline Ag material post-failure. Figure 6 illustrates instances of chemical clustering and short-range ordering observed within individual nanolayers. Heterogeneous distribution of Ag atoms within a nanolayer is evident from Figures 6(a)-(d), revealing Ag connections highlighted with yellow arrows between Ni-rich amorphous clusters. Each amorphous Ni cluster exhibits varying Ag composition, as demonstrated in Figure 6(e) and Supplementary Figures S10-S13, through brightness variations at different positions within the nanolayers. Furthermore, atomic-resolution STEM images in Figure 6(f) and Supplementary Figure S14 reveal the occurrence of short-range crystalline clusters (2-3 nm) within the amorphous nanolayers. It is worth noting that, although some crystalline clusters were also observed in the nanolayers of undeformed specimens, their number was noticeably higher in the deformed specimen.\u003c/p\u003e\n\u003cp\u003eMoving forward, to isolate the hardening effect of strain-induced CSRO in amorphous Ni-rich nanolayers, we investigated the mechanical behaviour of a hypothetical amorphous structure made with 100% Ni-9Ag alloy by hybrid MC/MD simulation. Our findings, illustrated in Figure 7(a)-(c), indicate two regimes of strain-induced phase transformation. Initially, there is a short-range ordering phase, wherein small amorphous and pure Ni clusters evolve into larger ones with increasing applied strain, up to 20%. Subsequently, dynamic recrystallization of the larger Ni clusters occurs, followed by the formation of amorphous pure Ag clusters within the amorphous Ni-Ag clusters as the strain surpasses 20%. Quantitative analysis presented in Figure 7(d) emphasizes the predominance of short-range ordering effects in the amorphous Ni-9Ag material until dynamic recrystallization takes place. Interestingly, the simulated stress-strain curves depicted in Figure 7(e) highlight a strong correlation between strain hardening and the initial CSRO stage during hybrid MC/MD simulation. This stands in contrast to the lack of strain hardening observed in the amorphous plastic flow simulated in the Ni-9Ag alloy without CSRO using the classical approach. The CSRO-induced hardening behaviour is different from Ni crystallization-induced hardening predicted in Figure 7(e) and Supplementary Figure S7. \u0026nbsp;In summary, our simulations provide direct evidence linking strain hardening behavior to strain-induced CSRO in the amorphous Ni-Ag nanolayers.\u0026nbsp;\u003c/p\u003e"},{"header":"Conclusion","content":"\u003cp\u003eWe have observed a nanoscale strengthening mechanism in both experiments and atomistic simulations in nanocrystalline Ag films by intercalation of ultrathin amorphous Ni-rich layers, which was found to fundamentally differ from grain-boundary and interface strengthening mechanisms seen in traditional nanolaminated metallic materials. The introduction of amorphous Ni-rich nanolayers simultaneously increased the grain stability, hardness, tensile yield strength, strain-hardening rates, and tensile ductility in nanocrystalline Ag, breaking record levels for this metal. The underlying strain-hardening mechanism was intrinsic to the amorphous Ni-rich nanolayer structure and resulted from chemical short-range ordering due to substantial quantities of Ag atoms mixed with the nanolayers at varying concentrations. This discovery is important for the development of tougher Ag film materials for deformable conductive electrodes with unprecedented mechanical and physical properties.\u003c/p\u003e"},{"header":"Methods","content":"\u003cp\u003e\u003cstrong\u003eMaterials synthesis.\u0026nbsp;\u003c/strong\u003eA\u0026nbsp;film sample of nanocrystalline Ag/amorphous Ni multilayer was synthesized by magnetron sputtering\u003csup\u003e47\u003c/sup\u003e onto a \u0026lt;100\u0026gt; oriented Si wafer. Three 50 mm diameter Ag targets were arranged in a confocal geometry to sputter onto a 152-mm diameter substrate, which was rotated at 15 revolutions per minute. The substrate was cooled by liquid N2. A fourth target of Ni metal, 76 mm in diameter, was also arranged in a confocal geometry outside the circle of Ag targets. For all sputtering runs, the base pressure was \u0026lt; 5 × 10\u003csup\u003e-8\u0026nbsp;\u003c/sup\u003etorr and the working pressure was 5 mtorr of Ar. The three sputtering guns with Ag targets were operated together for 2 seconds at 175 W, while the sputtering gun with the Ni target was operated for 20 s at 175 W. The sputtering rates were estimated to be 11.8 nm/s and 0.127 nm/s for the Ag and Ni layers, respectively. The deposited multilayer was 3.2 μm in total thickness as verified by field-emission scanning electron microscopy (FESEM).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eElectron microscopy.\u0026nbsp;\u003c/strong\u003eCross-sectional transmission electron microscope (TEM) samples were prepared by a focused ion beam instrument with a gas injection system (Helios, Thermo Fisher Scientific Ltd.). The TEM samples were then investigated by an aberration-corrected TEM (Titan Cube, Thermo Fisher Scientific Ltd.) at 200 kV. Energy-dispersive X-ray spectroscopy (EDS) studies were carried out with a Super-X EDX detector and GIF Quantum ER (965) system. Fracture surfaces after tensile testing were analysed by secondary electron imaging in a FESEM (Zeiss Sigma 300VP) operated at 5 kV.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eNanoindentation testing.\u0026nbsp;\u003c/strong\u003eNanoindentation experiments were carried out under displacement-control mode with a Hysitron Ti-750 nanomechanical testing system\u0026nbsp;(Eden Prairie, MN, USA) at the Manitoba Institute for Materials (MIM). The nanoindenter\u0026nbsp;used a Diamond Berkovich tip, which was repetitively loaded and then unloaded in 18 force increments up to a maximum force of 5 mN. The Oliver-Pharr method was used to extract the effective modulus and hardness. Indentations with different depths ranging from 100-300 nm were collected.\u0026nbsp;We found that the hardness values were stabilized at an indentation depth of 175 nm into the film. Each indentation was performed using a rectangular pattern with a minimum distance of 10 microns between each other to prevent the interference of the stress field caused by nearby indentations.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTensile mechanical testing.\u0026nbsp;\u003c/strong\u003eThe multilayered film was cut directly on the Si wafer into 25-mm-long strips using a 45-mm tungsten steel rotary blade (Olfa) and a flat metallic ruler (Westcott). This technique was found to significantly reduce surface defects introduced by other methods such as precision laser cutting. The width was 2.7 ± 0.01 mm as measured with an optical microscope at 100X magnification. The film strip was gently detached from the wafer using flat-ended tweezers. Square pieces of one-sided Cu tape were sticked at each end of the strip and carefully lifted to a mini-tensile testing machine with a 500 N load cell (Kammrath and Weiss). The strain rate was 10\u003csup\u003e-4\u003c/sup\u003e s\u003csup\u003e-1\u003c/sup\u003e. Testing was repeated three times to verify the reproducibility of the results. For comparison, the tensile behaviour of an annealed pure Ag foil of 50 microns in thickness (GoodFellow) was characterized using the same methodology. Strain hardening rates were calculated as a function of strain by fitting the stress-strain curve with a fourth-order polynomial function for strains between 0.01 and the maximum strain at failure and deriving this function.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eMD simulation.\u003c/strong\u003e MD simulations were performed using the Large-Scale Atomic/Molecular Massively Parallel Simulator (LAMMPS)\u003csup\u003e48\u003c/sup\u003e with a semi-empirical Finnis-Sinclair interatomic potential for Ag-Ni alloys developed by Pan et al.\u003csup\u003e31\u003c/sup\u003e. This potential was\u0026nbsp;fitted on ab initio calculations to accurately predict the stacking-fault energy curve, grain boundary energies and interface segregation energies of Ni atoms in FCC Ag. \u0026nbsp;Atomistic models were generated using the Atomsk software\u003csup\u003e49\u003c/sup\u003e. The simulation box was 52 nm × 52 nm × 52 nm. A set number of FCC Ag grains were placed with random distribution and random orientation by a Voronoi Tessellation algorithm. Perfectly coherent nanotwins were introduced with a constant twin boundary spacing of 2.8 nm. Other models were also created without nanotwins for comparison. Each boundary was defined as periodic. The final grain diameter after relaxation was quantified using the grain analysis in the atomic visualization software OVITO\u003csup\u003e50\u003c/sup\u003e. To create amorphous Ni-9Ag alloy layers, Ag atoms were removed in layers and replaced with crystalline FCC Ni atoms to obtain an estimate of the total Ni atoms required for the amorphous layer. After relaxation, the crystalline Ni layer compressed by ~1 nm. Accounting for this effect, the defined region to remove Ag atoms was increased to achieve the desired thickness as seen in the experiment. The model was then generated again by inserting 91% Ni and 9% Ag atoms in a random fashion to generate an amorphous layer. Each Ag/Ni model contained 8.13 million atoms and the pure nc-Ag models contained 7.81 million atoms.\u003c/p\u003e\n\u003cp\u003e\u0026nbsp; \u0026nbsp; \u0026nbsp;\u0026nbsp;Each model was first relaxed under isobaric-isothermal ensemble (NPT) at zero pressure and a temperature of 450 K for 100 ps, cooled to 300 K over 50 ps and then maintained at 300 K for another 50 ps. The time step was 5 fs. Subsequently, the model was deformed under compression by applying a constant engineering strain rate to the simulation box of 0.0001 ps\u003csup\u003e-1\u003c/sup\u003e in the negative z direction. For the classical simulation approach, deformation was performed under an NPT ensemble at 300 K with zero pressure in the x and y axes. To study CSRO with the hybrid MC/MD approach, we modified the variance-constrained semi-grand canonical ensemble algorithm described in Reference\u003csup\u003e32\u003c/sup\u003e by introducing deformation of the simulation box at constant strain rate and constant temperature (300 K). The atomic structure and short-range order were studied using the common-neighbor analysis and the polyhedral template matching analysis, respectively, in OVITO.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAcknowledgment:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eRP and FS received support by the U.S. Department of Energy (DOE) under grant no. DE-SC0020054 and used computational resources from the Extreme Science and Engineering Discovery Environment (XSEDE) supported by the National Science Foundation (NSF) under grant no. ACI-1548562 and the National Energy Research Scientific Computing Center (NERSC), a U.S. DOE Office of Science User Facility operated under contract no. DE-AC02-05CH11231. RTO and LZ acknowledge support from Laboratory Directed Research and Development at Ames National Laboratory, operated for the U.S. DOE by Iowa State University of Science and Technology under contract No. DE-AC02-07CH11358. YL and GZZ acknowledge support from the Natural Sciences and Engineering Research Council of Canada (NSERC). CD received support from the NSERC Discovery grant no. RGPIN-2019-05834. The field-emission SEM used in this study was acquired through NSF MRI grant no. 1828371.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor Contributions:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eFS and RO conceived the original hypothesis and managed the overall project. JO, LZ and RO produced the sputter deposited film and TEM/STEM images. YL, GZZ and CD conducted the nanoindentation experiments. FS conducted the tensile testing and FESEM. RP and FS performed and analyzed the atomistic simulations and wrote the manuscript. \u0026nbsp;All authors have contributed to the results discussion and given approval to the final version of the manuscript.\u003cstrong\u003e\u003cbr\u003e\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n \u003cli\u003eZ. Cheng, L. L., S. Xu, M. Lu and X. Wang. Temperature Dependence of Electrical and Thermal Conduction in Single Silver Nanowire. \u003cem\u003eScientific Reports\u003c/em\u003e \u003cstrong\u003e5\u003c/strong\u003e (2015).\u003c/li\u003e\n \u003cli\u003eKemp, W. R. G., Klemens, P. G., Sreedhar, A. K., White, G. K. \u0026amp; Simon, F. E. The thermal and electrical conductivity of silver-palladium and silver-cadmium alloys at low temperatures. \u003cem\u003eProceedings of the Royal Society of London. Series A. 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Eng.\u003c/em\u003e \u003cstrong\u003e18\u003c/strong\u003e (2010).\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":true,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":true,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Short-range order, hardening, tensile ductility, nanocrystalline metals, multilayers.","lastPublishedDoi":"10.21203/rs.3.rs-4402670/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-4402670/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eSilver, known for its high thermal and electrical conductivity, is an ideal metal for thin-film electrode applications. Because alloying can negatively affect conductivity, enhancing the strength and resistance to strain poses a tremendous challenge when applied to pure Ag films. Herein, in both experiments and atomistic simulations, we discover a nanoscale strengthening mechanism by intercalating ultrathin amorphous Ni-rich layers between pure nanocrystalline Ag films, resulting in the formation of a multilayered Ag and Ni-Ag alloy material with a stable grain size (22 nm) combining the highest hardness (2.6 GPa), tensile strength (677 MPa) and plastic elongation (6.6%) ever reported for this metal. The integration of amorphous Ni-Ag alloy nanolayers substantially improves the strain hardening behavior and extends the tensile ductility compared to standard crystalline Ag/Ni nanolaminates at an equivalent Ag layer thickness. This phenomenon results from strain-induced chemical short-range order within the amorphous Ni-Ag nanolayers during plastic deformation. The new nanoscale strengthening mechanism can be easily leveraged to develop nanocrystalline films with exceptional mechanical and physical properties.\u003c/p\u003e","manuscriptTitle":"Short-Range Order Enhances Strength and Tensile Ductility in Nanocrystalline Silver with Intercalation of Amorphous Nickel Nanolayers","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-05-30 09:33:38","doi":"10.21203/rs.3.rs-4402670/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"0798e2ff-c921-447c-936f-3703a41023e3","owner":[],"postedDate":"May 30th, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[{"id":32527371,"name":"Physical sciences/Materials science/Structural materials/Mechanical properties"},{"id":32527372,"name":"Physical sciences/Nanoscience and technology/Nanoscale materials"}],"tags":[],"updatedAt":"2024-07-23T14:45:14+00:00","versionOfRecord":[],"versionCreatedAt":"2024-05-30 09:33:38","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-4402670","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-4402670","identity":"rs-4402670","version":["v1"]},"buildId":"7rjqhiLT3MXkJMwkYKINL","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}