In-situ TEM Investigation of Stacking-Fault Intersection–Controlled Deformation in High-Mn TRIP Steel

In-situ TEM Investigation of Stacking-Fault Intersection–Controlled Deformation in High-Mn TRIP Steel | 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 Research Article In-situ TEM Investigation of Stacking-Fault Intersection–Controlled Deformation in High-Mn TRIP Steel Sung-Dae Kim This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-9026817/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 6 You are reading this latest preprint version Abstract The deformation behavior of a high-manganese transformation-induced plasticity (TRIP) steel was investigated using in-situ straining transmission electron microscopy (TEM), with emphasis on the dynamic interaction between stacking faults and partial dislocations during plastic deformation. Owing to the low stacking-fault energy of the alloy, plastic deformation is dominated by Shockley partial dislocations, leading to extensive stacking-fault formation on multiple {111} planes. As deformation proceeds, stacking faults generated on different slip variants frequently intersect within grain interiors. Real-time observations demonstrate that these intersections act as strong deformation-generated barriers that impede partial dislocation motion. The resulting dislocation pile-up and local strain concentration contribute significantly to the pronounced work-hardening capability of the TRIP steel. Despite this strong blocking effect, detailed in-situ analysis reveals that stacking-fault intersections are not strictly impenetrable. Under conditions of significant dislocation accumulation, the separation distance between leading and trailing partial dislocations can locally decrease, allowing their temporary recombination into a perfect dislocation segment. The recombined dislocation assumes screw character, which enables cross-slip onto a secondary {111} slip plane. After cross-slip, the perfect dislocation can redissociate into Shockley partial dislocations due to the low stacking-fault energy of the alloy, allowing glide to resume on the new slip plane. These observations demonstrate that stacking-fault intersections primarily function as strengthening barriers to partial dislocation motion, while occasionally enabling stress-assisted dislocation recombination and localized cross-slip. The present in-situ TEM results provide direct mechanistic insight into the dynamic interaction between stacking faults and dislocations and clarify how stacking-fault intersections influence both strain hardening and local plastic accommodation in high-Mn TRIP steels. High-manganese TRIP steel In-situ TEM Stacking fault interaction Partial dislocation Work hardening Figures Figure 1 Figure 2 Figure 3 Figure 4 1. Introduction High-manganese austenitic steels are widely studied for their exceptional combination of strength and ductility, which originates from their ability to maintain a high strain-hardening rate during plastic deformation [ 1 ]. In transformation-induced plasticity (TRIP) steels, this behavior is closely related to the stacking fault energy (SFE) of austenite, which governs partial dislocation activity, stacking fault formation, and strain-induced ε-martensitic transformation [ 2 – 5 ]. In low-SFE austenitic steels, plastic deformation is primarily accommodated by Shockley partial dislocations, leading to the accumulation of stacking faults on {111} planes. With increasing strain, interactions among stacking faults can promote the formation of continuous fault sequences that serve as precursors for ε-martensite [ 6 – 9 ]. While the importance of stacking faults in TRIP behavior is well recognized, the dynamic interactions between stacking faults formed on different {111} planes and their influence on partial dislocation mobility remain insufficiently understood. Most previous investigations have relied on post-mortem microstructural characterization, which provides only static information after deformation [ 10 – 12 ]. Consequently, direct experimental evidence linking stacking-fault interactions to dislocation-level strain hardening is limited. In particular, the role of stacking-fault intersections as dynamic obstacles to partial dislocation motion, and the conditions under which partial dislocations may locally overcome these obstacles, have not been clearly established. In this study, in-situ straining transmission electron microscopy is employed to directly observe the deformation behavior of a high-Mn TRIP steel in real time. The evolution of partial dislocations, stacking faults, and their intersections on multiple {111} planes is captured during deformation. The results demonstrate that stacking-fault intersections act as dominant, deformation-generated barriers to partial dislocation motion, thereby enhancing work hardening, while also permitting localized and transient cross-slip under extreme local stress conditions. These findings provide new mechanistic insight into the interplay between stacking-fault interactions, strain hardening, and transformation behavior in high-Mn TRIP steels. 2. Experimental Methods A representative high-manganese austenitic TRIP steel was selected for the present study. The nominal chemical composition was Fe–25Mn–0.4C (wt.%), designed to stabilize austenite at room temperature while maintaining a low stacking fault energy (SFE) favorable for stacking fault formation and strain-induced ε-martensitic transformation. The alloy was produced by vacuum induction melting and cast into ingots. After homogenization at 1200°C for 5 h, the ingots were hot-forged into plates and solution-treated at 1050°C for 1 h followed by water quenching to suppress carbide precipitation and retain a fully austenitic microstructure prior to deformation. Thin foils for transmission electron microscopy were prepared by mechanical grinding followed by twin-jet electrochemical polishing. For in-situ straining TEM experiments, elongated strip-type specimens (~ 3 mm × 12 mm) were fabricated from the polished foils using a custom punching method. The specimen geometry and preparation procedure were adapted from previously reported in-situ TEM studies on high-Mn steels. The punched samples were electropolished using a perchloric acid–methanol (9:1) solution at − 20°C to obtain electron-transparent regions (TenuPol-5, Struers). For post-mortem analysis of the deformed samples, discs with a diameter of 3 mm were punched from the deformed samples. Transmission electron microscopy was carried out at an accelerating voltage of 200 kV (JEM-2100F, JEOL Ltd.). Bright-field (BF) imaging conditions were primarily employed to visualize dislocation activity and stacking fault formation with high temporal resolution. In-situ straining TEM experiments were performed using a dedicated straining holder (model 654, Gatan), enabling controlled tensile deformation inside the TEM column. Deformation was applied under displacement-controlled conditions to allow quasi-static loading while continuously observing microstructural evolution. Real-time TEM videos were recorded during deformation to capture the nucleation, glide, and interaction of partial dislocations and the associated formation of stacking faults (Camtasia studio, TechSmith). Observations focused on grains oriented near low-index zone axes, enabling clear identification of stacking faults formed on different {111} planes and their intersections. Low-angle annular dark-field scanning transmission electron microscopy (LAADF-STEM) images were acquired using an annular detector with a typical inner collection angle of ~ 20–30 mrad, providing contrast sensitive to lattice strain and atomic displacement. Regions containing intersecting stacking faults were identified by conventional TEM and subsequently examined by LAADF-STEM. 3. Results and Discussion Figure 1 and Supplementary Video S1 demonstrate that plastic deformation in the investigated high-Mn TRIP steel is governed predominantly by Shockley partial dislocation activity. Immediately after yielding, numerous dislocation segments are nucleated and propagate over extended distances (Fig. 1 (a) ). Burgers vector analysis confirms that these dislocations correspond to 1/6⟨112⟩ Shockley partials rather than perfect dislocations. Each moving partial leaves behind a planar defect consistent with a stacking fault (SF), indicating that plastic strain is primarily accommodated through stacking-fault formation. The dominance of partial dislocations is consistent with the low stacking-fault energy (SFE) of the present alloy (~ 20 mJ·m⁻²), which promotes wide dissociation of perfect dislocations into leading and trailing partials [ 13 , 14 ]. In contrast to moderate- or high-SFE FCC alloys—where the trailing partial readily follows the leading partial and restores perfect stacking—the present in-situ observations show that trailing partial motion is frequently suppressed. Consequently, stacking faults remain stable and accumulate progressively with increasing strain. As deformation proceeds, SFs form on multiple {111} planes within individual grains (Fig. 1 (b) ). Activation of multiple slip variants leads to the development of a three-dimensional network of intersecting stacking faults. This multi-variant stacking-fault configuration provides the microstructural framework for the intersection-controlled deformation behavior discussed below. During continued straining, partial dislocations gliding on a given {111} plane are frequently observed to decelerate or become arrested when encountering a stacking fault formed on a different {111} plane (Fig. 2 (a) ). Because the process is captured in real time ( Supplementary Video S2 ), the causal relationship is unequivocal: obstruction occurs precisely at the geometric intersection between stacking faults. These interactions take place entirely within grain interiors and evolve dynamically during deformation, ruling out conventional obstacles such as precipitates or grain boundaries. This blocking behavior is consistent with the established understanding that Shockley partial dislocations are crystallographically confined to their original {111} planes and possess intrinsically limited cross-slip capability in low-SFE alloys. Cross-slip requires recombination of leading and trailing partials into a perfect dislocation, followed by redissociation on another {111} plane—a process that is energetically unfavorable under typical conditions [ 13 , 15 ]. Consequently, stacking-fault intersections act as strong geometric barriers to partial dislocation glide. LAADF-STEM analysis further supports this interpretation. In LAADF mode, image intensity is sensitive to strain-induced diffuse scattering; regions exhibiting greater lattice distortion appear brighter [ 16 , 17 ]. The pronounced intensity enhancement observed at SF intersections (Fig. 2 (b) ) indicates significant local strain accumulation. Such strain concentration further increases the energetic barrier for dislocation transmission across the intersection. As deformation proceeds and the density of stacking faults increases, the number of intersection sites correspondingly rises. These intersections therefore constitute deformation-generated obstacles that continuously emerge during plastic flow. The resulting accumulation of partial dislocations at these sites enhances local stress concentration and contributes substantially to the high work-hardening capability characteristic of TRIP steels. Up to this point, the present observations directly confirm the widely recognized role of stacking-fault intersections as strengthening elements in low-SFE alloys [ 1 – 4 , 6 – 9 , 18 , 19 ]. While stacking-fault intersections primarily function as strong barriers, detailed in-situ observations ( Supplementary Videos S3 & S4 ) reveal that they are not strictly impenetrable. In a limited number of cases, localized and transient cross-slip events are observed at intersection sites after significant dislocation accumulation. Frame-by-frame analysis (Fig. 3 ) indicates that such events occur only after pronounced pile-up of partial dislocations at a given intersection. The resulting stress concentration locally reduces the separation distance between the leading and trailing partials, facilitating their temporary recombination into a perfect dislocation segment. Importantly, this recombined segment remains pinned at the intersection, which serves as a fixed anchoring point. According to the Thomson tetrahedron construction, recombination of two Shockley partial dislocations on a given {111} slip system produces a perfect dislocation with a ⟨110⟩ Burgers vector ( b ). At the intersection geometry observed here, the line direction ( u ) of the recombined segment coincides with this ⟨110⟩ direction. Consequently, the recombined perfect dislocation inherently assumes screw character, with the line vector ( u ) parallel to the Burgers vector ( b ) (i.e., u ∥ b ) immediately upon recombination. Because screw dislocations in FCC crystals can cross-slip between equivalent {111} planes, this configuration renders cross-slip onto a secondary {111} variant crystallographically permissible [ 13 , 15 ]. Once transferred to the secondary slip plane, the perfect dislocation segment can again dissociate into leading and trailing Shockley partials due to the low stacking-fault energy of the alloy. The re-formed partial dislocations then resume glide on the secondary variant, leaving behind a stacking fault on that plane. Thus, the observed cross-slip originates from partial recombination that inherently produces a screw-type perfect dislocation at the intersection. The overall sequence can therefore be summarized as (Fig. 4 ): partial blocking → stress accumulation → recombination into a screw-type perfect dislocation → cross-slip → redissociation into partial dislocations on the secondary plane. The present results refine the conventional picture of stacking-fault intersections in TRIP steels. Their primary and dominant role is to impede partial dislocation motion, promote dislocation pile-up, and enhance work hardening. This strengthening effect arises from both crystallographic confinement of partial dislocations and strain concentration at intersection sites. However, the in-situ observations demonstrate that under sufficiently high local stress, these same intersections can act as sites of stress-induced dislocation character transformation. The inability of partial dislocations to readily cross-slip enables substantial stress accumulation, which in turn drives recombination and screw-segment formation, ultimately permitting localized cross-slip. Therefore, stacking-fault intersections exhibit a dual but asymmetric mechanical function: they primarily serve as strengthening barriers, while secondarily enabling stress-activated dislocation reconfiguration when a critical local stress threshold is exceeded. The cross-slip events are spatially limited and transient, and do not negate the overall hardening effect; instead, they provide a localized stress-relief pathway within an otherwise strongly hardened microstructure. By directly visualizing this dynamic transition in real time, the present study extends the understanding of intersection-controlled plasticity beyond static blocking and reveals the underlying mechanism by which extreme local stresses can trigger dislocation character transformation in low-SFE TRIP steels. 4. Conclusions In this study, the deformation behavior of a high-Mn TRIP steel was investigated by in-situ straining transmission electron microscopy, with particular focus on the dynamic role of stacking-fault (SF) intersections during plastic deformation. The main findings are summarized as follows: Plastic deformation is dominated by Shockley partial dislocations due to the low stacking-fault energy of the alloy, leading to extensive stacking-fault formation on multiple {111} planes and the development of a three-dimensional network of intersecting faults. Stacking faults formed on different {111} planes frequently intersect within grain interiors. Real-time TEM observations directly confirm that these intersections act as strong deformation-generated barriers to partial dislocation motion. The resulting dislocation pile-up and local strain concentration contribute significantly to the pronounced work-hardening behavior of the TRIP steel. Although SF intersections primarily function as strengthening obstacles, localized and transient cross-slip events can occur under sufficiently high local stress conditions. These events are initiated by stress-assisted recombination of leading and trailing partial dislocations into a perfect dislocation segment, followed by rotation of the dislocation line into screw character ( u ∥ b ), which enables cross-slip onto an alternative {111} plane. The observed cross-slip does not reflect intrinsically facile partial dislocation motion in low-SFE alloys. Rather, it represents a stress-activated dislocation character transformation that occurs only after substantial stress accumulation at SF intersections. Overall, the present in-situ observations demonstrate that stacking-fault intersections in TRIP steel exhibit a dual but asymmetric mechanical role: they primarily enhance strength by blocking partial dislocation glide, while secondarily providing a localized, stress-driven pathway for dislocation reconfiguration. These findings refine the mechanistic understanding of intersection-controlled plasticity and highlight the dynamic nature of dislocation processes in low-SFE austenitic steels. Declarations Acknowledgments This work was supported by a Research Grant of Pukyong National University(2025). Authors' contributions S.D. Kim conceived the study, designed the experiments, performed the in-situ TEM experiments, analyzed the data, and wrote the manuscript. The author read and approved the final manuscript. Competing interests The author declares that he has no competing interests. Funding This work was supported by a Research Grant of Pukyong National University (2025). Availability of data and materials The datasets generated during the current study are available from the corresponding author on reasonable request. References O. Grässel, L. Krüger, G. Frommeyer, and L.W. Meyer, High strength Fe–Mn–(Al, Si) TRIP/TWIP steels development—properties and applications, Int. J. Plasticity 16 , 1391–1409 (2000). K.T. Park, K.G. Jin, S.H. Han, S.W. Hwang, and C.S. Lee, Stacking fault energy and plastic deformation of fully austenitic high manganese steels: Effect of Al addition, Mater. Sci. Eng. A 527 , 3651–3658 (2010). D.T. Pierce, D. Raabe, J.A. Jiménez, J. Bentley, and J.E. Wittig, The influence of manganese content on the stacking fault and austenite/ε-martensite interfacial energies in Fe–Mn steels, Acta Mater. 68 , 238–253 (2014). I. Gutierrez-Urrutia and D. Raabe, Dislocation and twin substructure evolution during strain hardening of an Fe–22Mn–0.6C TWIP steel, Acta Mater. 60 , 5791–5802 (2012). T.S. Byun, On the stress dependence of partial dislocation separation and deformation twinning in FCC metals, Acta Mater. 51 , 3063–3071 (2003). S. Allain, J.P. Chateau, O. Bouaziz, S. Migot, and N. Guelton, Correlations between the calculated stacking fault energy and the plasticity mechanisms in Fe–Mn–C alloys, Mater. Sci. Eng. A 387–389 , 158–162 (2004). H.K. Kim, S.H. Kim, and J.P. Ahn, Methods to evaluate the twin formation energy: comparative studies of atomic simulations and in-situ TEM tensile tests, Appl. Microsc. 50 , 19 (2020). https://doi.org/10.1186/s42649-020-00039-2 B.C. De Cooman, Y. Estrin, and S.K. Kim, Twinning-induced plasticity (TWIP) steels, Acta Mater. 142 , 283–362 (2018). Ko, K.K., Jang, J.H., Tiwari, S. et al. Quantitative analysis of retained austenite in Nb added Fe-based alloy. Appl. Microsc. 52 , 5 (2022). https://doi.org/10.1186/s42649-022-00074-1 H. Idrissi, K. Renard, L. Ryelandt, D. Schryvers, and P.J. Jacques, On the mechanism of twin formation in Fe–Mn–C TWIP steels, Acta Mater. 58 , 2464-2476 (2010). M. Koyama, T. Sawaguchi, T. Lee, C.S. Lee, and K. Tsuzaki, Work hardening associated with martensitic transformation, twinning, and dislocation glide in metastable austenitic steels, Mater. Sci. Eng. A 528 , 7310–7316 (2011). J. Talonen and H. Hänninen, Formation of shear bands and strain-induced martensite during plastic deformation of metastable austenitic stainless steel, Acta Mater. 55 , 6108–6118 (2007). D. Hull and D.J. Bacon, Introduction to Dislocations , 5th ed., Butterworth-Heinemann, Oxford (2011). A. Dumay, J.P. Chateau, S. Allain, S. Migot, and O. Bouaziz, Influence of addition elements on the stacking fault energy and mechanical properties of an austenitic Fe–Mn–C steel, Mater. Sci. Eng. A 483–484 , 184–187 (2008). J.P. Hirth and J. Lothe, Theory of Dislocations , 2nd ed., Wiley, New York (1982). S.J. Pennycook and P.D. Nellist, Scanning Transmission Electron Microscopy: Imaging and Analysis , Springer, New York (2011). P.E. Batson, N. Dellby, and O.L. Krivanek, Sub-angstrom resolution using aberration corrected electron optics, Nature 418 , 617–620 (2002). J.K. Kim, Y. Estrin, and B.C. De Cooman, Constitutive modeling of the stacking fault energy-dependent deformation behavior of Fe–Mn–C TWIP steels, Metall. Mater. Trans. A 49 , 5919–5924 (2018). Z. Li, Y. Zhao, and J. Li, The influence of stacking faults on mechanical behavior of advanced materials: A review, Mater. Sci. Eng. A 789 , 139660 (2020). Supplementary Files SV1.avi Supplementary Video S1. Real-time in-situ TEM observation of partial dislocation nucleation and glide in high-manganese TRIP steel during tensile deformation. The video shows the initial formation of stacking faults and the propagation of leading partial dislocations along {111} slip planes. SV2.avi Supplementary Video S2. In-situ TEM recording showing interactions between moving partial dislocations and pre-existing stacking faults. Dislocation blocking and pile-up at stacking-fault intersections are observed, illustrating the role of stacking-fault interactions in strain hardening. SV3.avi Supplementary Video S3 & S4. In-situ TEM observation of the same mechanism, highlighting the cross-slip process of partial dislocations initially pinned at the stacking-fault intersection. After cross slip to another variant, the dislocations propagate and generate a stacking fault on the adjacent plane. SV4.avi Supplementary Video S3 & S4. In-situ TEM observation of the same mechanism, highlighting the cross-slip process of partial dislocations initially pinned at the stacking-fault intersection. After cross slip to another variant, the dislocations propagate and generate a stacking fault on the adjacent plane. Cite Share Download PDF Status: Under Review Version 1 posted Editorial decision: Major revision 23 Mar, 2026 Reviewers agreed at journal 08 Mar, 2026 Reviewers invited by journal 05 Mar, 2026 Editor invited by journal 05 Mar, 2026 Editor assigned by journal 05 Mar, 2026 First submitted to journal 03 Mar, 2026 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-9026817","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":601560344,"identity":"77a5a662-1ccd-4929-ad3f-509a7d50fcb1","order_by":0,"name":"Sung-Dae Kim","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAAvUlEQVRIiWNgGAWjYFCCNIYDDBUMBlBeArFazpCqhYGxjRQt8u1piYduzrtjbC6RwPjhB0NaPkEtBmeeHTicu+2ZmeWMBGbJHoYcywaCWiTSG4BaDtsY3EhgkGZgqDAgpINBfgZIyxywFubfRGlhuJEGdFjDYTOgFjagLTmEtQD9knA459gzY4MzD9ssewzSiHBYe5rx55yaO4YbjicfvvGjIpkIh0HAASBmbGBgIFoDRMsoGAWjYBSMAhwAADTJQIK3Imr8AAAAAElFTkSuQmCC","orcid":"","institution":"Pukyong National University","correspondingAuthor":true,"prefix":"","firstName":"Sung-Dae","middleName":"","lastName":"Kim","suffix":""}],"badges":[],"createdAt":"2026-03-04 07:07:45","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-9026817/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-9026817/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":104442448,"identity":"9990bfe5-f52a-4a82-9428-afccfd0837f7","added_by":"auto","created_at":"2026-03-11 18:53:02","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":508785,"visible":true,"origin":"","legend":"\u003cp\u003e(a) Bright-field TEM image showing the nucleation and glide of Shockley partial dislocations after yielding. Each partial leaves behind a stacking fault (SF), indicating that plastic deformation is primarily accommodated through stacking-fault formation. (b) Formation of stacking faults on multiple {111} planes within a single grain. Activation of different slip variants results in intersecting stacking faults, establishing a three-dimensional fault network during deformation.\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-9026817/v1/31a747df48e95cfb46efe85e.png"},{"id":104442450,"identity":"e181d0bf-b99f-43e5-8aa0-0cdd60574b5f","added_by":"auto","created_at":"2026-03-11 18:53:02","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":1013091,"visible":true,"origin":"","legend":"\u003cp\u003e(a) In-situ TEM image showing a partial dislocation gliding on a {111} plane being arrested at the geometric intersection with a stacking fault formed on a different {111} variant (highlighted region). Real-time observation confirms that the obstruction occurs precisely at the intersection site.\u003cbr\u003e\n(b) LAADF-STEM image of an SF intersection. The enhanced intensity at the intersection indicates significant local lattice distortion and strain accumulation, supporting its role as a strong deformation-generated barrier to partial dislocation motion.\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-9026817/v1/90e4832d67b9350645e9391a.png"},{"id":104442449,"identity":"c05c20f0-8053-4df7-b524-623769142645","added_by":"auto","created_at":"2026-03-11 18:53:02","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":743085,"visible":true,"origin":"","legend":"\u003cp\u003eSequential TEM images showing (i) accumulation of partial dislocations at the intersection, (ii) stress-assisted recombination of leading and trailing partials into a perfect dislocation segment, (iii) formation of a screw-type perfect dislocation (\u003cstrong\u003eu\u003c/strong\u003e ∥ \u003cstrong\u003eb\u003c/strong\u003e), and (iv) cross-slip onto a secondary {111} plane. After cross-slip, the dislocation redissociates into partial dislocations on the new slip plane.\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-9026817/v1/2f155256d38741589046b9b0.png"},{"id":104442451,"identity":"ae83541c-f782-41cd-a1ad-a2a51b8a3f67","added_by":"auto","created_at":"2026-03-11 18:53:02","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":265540,"visible":true,"origin":"","legend":"\u003cp\u003eSchematic illustration of dislocation evolution at a stacking-fault intersection represented on a Thomson tetrahedron. Partial dislocations gliding on a primary {111} plane accumulate at the intersection and recombine to form a perfect dislocation with a ⟨110⟩ Burgers vector. Owing to the intersection geometry, the recombined segment assumes screw character (\u003cstrong\u003eu\u003c/strong\u003e ∥ \u003cstrong\u003eb\u003c/strong\u003e), enabling cross-slip onto a secondary {111} plane. On the secondary plane, the perfect dislocation redissociates into leading and trailing Shockley partials due to the low stacking-fault energy of the alloy.\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-9026817/v1/d99d914a70a528c307062fa7.png"},{"id":104785906,"identity":"c1dc09f7-96ce-464d-b3a6-9a0c13b14e3a","added_by":"auto","created_at":"2026-03-17 08:13:34","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":3292982,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-9026817/v1/0a40a8cc-4116-426a-b905-621c33acc200.pdf"},{"id":104442454,"identity":"61183a2d-abd6-4f7b-a934-2066e7389352","added_by":"auto","created_at":"2026-03-11 18:53:03","extension":"avi","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":6676302,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eSupplementary Video S1.\u003c/strong\u003e\u003cbr\u003e\nReal-time in-situ TEM observation of partial dislocation nucleation and glide in high-manganese TRIP steel during tensile deformation. The video shows the initial formation of stacking faults and the propagation of leading partial dislocations along {111} slip planes.\u003c/p\u003e","description":"","filename":"SV1.avi","url":"https://assets-eu.researchsquare.com/files/rs-9026817/v1/ce6029e73df80bff84c3b6b6.avi"},{"id":104442453,"identity":"b78abd1c-1b5c-4251-9211-207636340b45","added_by":"auto","created_at":"2026-03-11 18:53:03","extension":"avi","order_by":2,"title":"","display":"","copyAsset":false,"role":"supplement","size":6607626,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eSupplementary Video S2.\u003c/strong\u003e\u003cbr\u003e\nIn-situ TEM recording showing interactions between moving partial dislocations and pre-existing stacking faults. Dislocation blocking and pile-up at stacking-fault intersections are observed, illustrating the role of stacking-fault interactions in strain hardening.\u003c/p\u003e","description":"","filename":"SV2.avi","url":"https://assets-eu.researchsquare.com/files/rs-9026817/v1/e94c4cb8f2ada0f3321e4fa2.avi"},{"id":104780404,"identity":"58394932-028d-4c62-a2a5-4022f0bec96d","added_by":"auto","created_at":"2026-03-17 07:52:48","extension":"avi","order_by":3,"title":"","display":"","copyAsset":false,"role":"supplement","size":7362512,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eSupplementary Video S3 \u0026amp; S4.\u003c/strong\u003e\u003cbr\u003e\nIn-situ TEM observation of the same mechanism, highlighting the cross-slip process of partial dislocations initially pinned at the stacking-fault intersection. After cross slip to another variant, the dislocations propagate and generate a stacking fault on the adjacent plane.\u003c/p\u003e","description":"","filename":"SV3.avi","url":"https://assets-eu.researchsquare.com/files/rs-9026817/v1/7e7847a67776055d02ba75b0.avi"},{"id":104442455,"identity":"077131cc-f292-4285-b803-f5c92c1a1be4","added_by":"auto","created_at":"2026-03-11 18:53:03","extension":"avi","order_by":4,"title":"","display":"","copyAsset":false,"role":"supplement","size":26404822,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eSupplementary Video S3 \u0026amp; S4.\u003c/strong\u003e\u003cbr\u003e\nIn-situ TEM observation of the same mechanism, highlighting the cross-slip process of partial dislocations initially pinned at the stacking-fault intersection. After cross slip to another variant, the dislocations propagate and generate a stacking fault on the adjacent plane.\u003c/p\u003e","description":"","filename":"SV4.avi","url":"https://assets-eu.researchsquare.com/files/rs-9026817/v1/3fa12d9d307ad4698da8f3d8.avi"}],"financialInterests":"","formattedTitle":"In-situ TEM Investigation of Stacking-Fault Intersection–Controlled Deformation in High-Mn TRIP Steel","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eHigh-manganese austenitic steels are widely studied for their exceptional combination of strength and ductility, which originates from their ability to maintain a high strain-hardening rate during plastic deformation [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]. In transformation-induced plasticity (TRIP) steels, this behavior is closely related to the stacking fault energy (SFE) of austenite, which governs partial dislocation activity, stacking fault formation, and strain-induced ε-martensitic transformation [\u003cspan additionalcitationids=\"CR3 CR4\" citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eIn low-SFE austenitic steels, plastic deformation is primarily accommodated by Shockley partial dislocations, leading to the accumulation of stacking faults on {111} planes. With increasing strain, interactions among stacking faults can promote the formation of continuous fault sequences that serve as precursors for ε-martensite [\u003cspan additionalcitationids=\"CR7 CR8\" citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]. While the importance of stacking faults in TRIP behavior is well recognized, the dynamic interactions between stacking faults formed on different {111} planes and their influence on partial dislocation mobility remain insufficiently understood.\u003c/p\u003e \u003cp\u003eMost previous investigations have relied on post-mortem microstructural characterization, which provides only static information after deformation [\u003cspan additionalcitationids=\"CR11\" citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]. Consequently, direct experimental evidence linking stacking-fault interactions to dislocation-level strain hardening is limited. In particular, the role of stacking-fault intersections as dynamic obstacles to partial dislocation motion, and the conditions under which partial dislocations may locally overcome these obstacles, have not been clearly established.\u003c/p\u003e \u003cp\u003eIn this study, in-situ straining transmission electron microscopy is employed to directly observe the deformation behavior of a high-Mn TRIP steel in real time. The evolution of partial dislocations, stacking faults, and their intersections on multiple {111} planes is captured during deformation. The results demonstrate that stacking-fault intersections act as dominant, deformation-generated barriers to partial dislocation motion, thereby enhancing work hardening, while also permitting localized and transient cross-slip under extreme local stress conditions. These findings provide new mechanistic insight into the interplay between stacking-fault interactions, strain hardening, and transformation behavior in high-Mn TRIP steels.\u003c/p\u003e"},{"header":"2. Experimental Methods","content":"\u003cp\u003eA representative high-manganese austenitic TRIP steel was selected for the present study. The nominal chemical composition was Fe\u0026ndash;25Mn\u0026ndash;0.4C (wt.%), designed to stabilize austenite at room temperature while maintaining a low stacking fault energy (SFE) favorable for stacking fault formation and strain-induced ε-martensitic transformation. The alloy was produced by vacuum induction melting and cast into ingots. After homogenization at 1200\u0026deg;C for 5 h, the ingots were hot-forged into plates and solution-treated at 1050\u0026deg;C for 1 h followed by water quenching to suppress carbide precipitation and retain a fully austenitic microstructure prior to deformation.\u003c/p\u003e \u003cp\u003eThin foils for transmission electron microscopy were prepared by mechanical grinding followed by twin-jet electrochemical polishing. For in-situ straining TEM experiments, elongated strip-type specimens (~\u0026thinsp;3 mm \u0026times; 12 mm) were fabricated from the polished foils using a custom punching method. The specimen geometry and preparation procedure were adapted from previously reported in-situ TEM studies on high-Mn steels. The punched samples were electropolished using a perchloric acid\u0026ndash;methanol (9:1) solution at \u0026minus;\u0026thinsp;20\u0026deg;C to obtain electron-transparent regions (TenuPol-5, Struers). For post-mortem analysis of the deformed samples, discs with a diameter of 3 mm were punched from the deformed samples.\u003c/p\u003e \u003cp\u003eTransmission electron microscopy was carried out at an accelerating voltage of 200 kV (JEM-2100F, JEOL Ltd.). Bright-field (BF) imaging conditions were primarily employed to visualize dislocation activity and stacking fault formation with high temporal resolution. In-situ straining TEM experiments were performed using a dedicated straining holder (model 654, Gatan), enabling controlled tensile deformation inside the TEM column. Deformation was applied under displacement-controlled conditions to allow quasi-static loading while continuously observing microstructural evolution. Real-time TEM videos were recorded during deformation to capture the nucleation, glide, and interaction of partial dislocations and the associated formation of stacking faults (Camtasia studio, TechSmith). Observations focused on grains oriented near low-index zone axes, enabling clear identification of stacking faults formed on different {111} planes and their intersections. Low-angle annular dark-field scanning transmission electron microscopy (LAADF-STEM) images were acquired using an annular detector with a typical inner collection angle of ~\u0026thinsp;20\u0026ndash;30 mrad, providing contrast sensitive to lattice strain and atomic displacement. Regions containing intersecting stacking faults were identified by conventional TEM and subsequently examined by LAADF-STEM.\u003c/p\u003e"},{"header":"3. Results and Discussion","content":"\u003cp\u003eFigure \u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e and \u003cb\u003eSupplementary Video S1\u003c/b\u003e demonstrate that plastic deformation in the investigated high-Mn TRIP steel is governed predominantly by Shockley partial dislocation activity. Immediately after yielding, numerous dislocation segments are nucleated and propagate over extended distances (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e\u003cb\u003e(a)\u003c/b\u003e). Burgers vector analysis confirms that these dislocations correspond to 1/6⟨112⟩ Shockley partials rather than perfect dislocations. Each moving partial leaves behind a planar defect consistent with a stacking fault (SF), indicating that plastic strain is primarily accommodated through stacking-fault formation. The dominance of partial dislocations is consistent with the low stacking-fault energy (SFE) of the present alloy (~\u0026thinsp;20 mJ\u0026middot;m⁻\u0026sup2;), which promotes wide dissociation of perfect dislocations into leading and trailing partials [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e, \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e]. In contrast to moderate- or high-SFE FCC alloys\u0026mdash;where the trailing partial readily follows the leading partial and restores perfect stacking\u0026mdash;the present in-situ observations show that trailing partial motion is frequently suppressed. Consequently, stacking faults remain stable and accumulate progressively with increasing strain. As deformation proceeds, SFs form on multiple {111} planes within individual grains (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e\u003cb\u003e(b)\u003c/b\u003e). Activation of multiple slip variants leads to the development of a three-dimensional network of intersecting stacking faults. This multi-variant stacking-fault configuration provides the microstructural framework for the intersection-controlled deformation behavior discussed below.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eDuring continued straining, partial dislocations gliding on a given {111} plane are frequently observed to decelerate or become arrested when encountering a stacking fault formed on a different {111} plane (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e\u003cb\u003e(a)\u003c/b\u003e). Because the process is captured in real time (\u003cb\u003eSupplementary Video S2\u003c/b\u003e), the causal relationship is unequivocal: obstruction occurs precisely at the geometric intersection between stacking faults. These interactions take place entirely within grain interiors and evolve dynamically during deformation, ruling out conventional obstacles such as precipitates or grain boundaries. This blocking behavior is consistent with the established understanding that Shockley partial dislocations are crystallographically confined to their original {111} planes and possess intrinsically limited cross-slip capability in low-SFE alloys. Cross-slip requires recombination of leading and trailing partials into a perfect dislocation, followed by redissociation on another {111} plane\u0026mdash;a process that is energetically unfavorable under typical conditions [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e, \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e]. Consequently, stacking-fault intersections act as strong geometric barriers to partial dislocation glide. LAADF-STEM analysis further supports this interpretation. In LAADF mode, image intensity is sensitive to strain-induced diffuse scattering; regions exhibiting greater lattice distortion appear brighter [\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e, \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e]. The pronounced intensity enhancement observed at SF intersections (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e\u003cb\u003e(b)\u003c/b\u003e) indicates significant local strain accumulation. Such strain concentration further increases the energetic barrier for dislocation transmission across the intersection. As deformation proceeds and the density of stacking faults increases, the number of intersection sites correspondingly rises. These intersections therefore constitute deformation-generated obstacles that continuously emerge during plastic flow. The resulting accumulation of partial dislocations at these sites enhances local stress concentration and contributes substantially to the high work-hardening capability characteristic of TRIP steels. Up to this point, the present observations directly confirm the widely recognized role of stacking-fault intersections as strengthening elements in low-SFE alloys [\u003cspan additionalcitationids=\"CR2 CR3\" citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e, \u003cspan additionalcitationids=\"CR7 CR8\" citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e, \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e, \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e].\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eWhile stacking-fault intersections primarily function as strong barriers, detailed in-situ observations (\u003cb\u003eSupplementary Videos S3 \u0026amp; S4\u003c/b\u003e) reveal that they are not strictly impenetrable. In a limited number of cases, localized and transient cross-slip events are observed at intersection sites after significant dislocation accumulation. Frame-by-frame analysis (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e) indicates that such events occur only after pronounced pile-up of partial dislocations at a given intersection. The resulting stress concentration locally reduces the separation distance between the leading and trailing partials, facilitating their temporary recombination into a perfect dislocation segment. Importantly, this recombined segment remains pinned at the intersection, which serves as a fixed anchoring point. According to the Thomson tetrahedron construction, recombination of two Shockley partial dislocations on a given {111} slip system produces a perfect dislocation with a ⟨110⟩ Burgers vector (\u003cb\u003eb\u003c/b\u003e). At the intersection geometry observed here, the line direction (\u003cb\u003eu\u003c/b\u003e) of the recombined segment coincides with this ⟨110⟩ direction. Consequently, the recombined perfect dislocation inherently assumes screw character, with the line vector (\u003cb\u003eu\u003c/b\u003e) parallel to the Burgers vector (\u003cb\u003eb\u003c/b\u003e) (i.e., \u003cb\u003eu\u003c/b\u003e ∥ \u003cb\u003eb\u003c/b\u003e) immediately upon recombination. Because screw dislocations in FCC crystals can cross-slip between equivalent {111} planes, this configuration renders cross-slip onto a secondary {111} variant crystallographically permissible [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e, \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e]. Once transferred to the secondary slip plane, the perfect dislocation segment can again dissociate into leading and trailing Shockley partials due to the low stacking-fault energy of the alloy. The re-formed partial dislocations then resume glide on the secondary variant, leaving behind a stacking fault on that plane. Thus, the observed cross-slip originates from partial recombination that inherently produces a screw-type perfect dislocation at the intersection. The overall sequence can therefore be summarized as (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e): partial blocking \u0026rarr; stress accumulation \u0026rarr; recombination into a screw-type perfect dislocation \u0026rarr; cross-slip \u0026rarr; redissociation into partial dislocations on the secondary plane.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe present results refine the conventional picture of stacking-fault intersections in TRIP steels. Their primary and dominant role is to impede partial dislocation motion, promote dislocation pile-up, and enhance work hardening. This strengthening effect arises from both crystallographic confinement of partial dislocations and strain concentration at intersection sites. However, the in-situ observations demonstrate that under sufficiently high local stress, these same intersections can act as sites of stress-induced dislocation character transformation. The inability of partial dislocations to readily cross-slip enables substantial stress accumulation, which in turn drives recombination and screw-segment formation, ultimately permitting localized cross-slip. Therefore, stacking-fault intersections exhibit a dual but asymmetric mechanical function: they primarily serve as strengthening barriers, while secondarily enabling stress-activated dislocation reconfiguration when a critical local stress threshold is exceeded. The cross-slip events are spatially limited and transient, and do not negate the overall hardening effect; instead, they provide a localized stress-relief pathway within an otherwise strongly hardened microstructure. By directly visualizing this dynamic transition in real time, the present study extends the understanding of intersection-controlled plasticity beyond static blocking and reveals the underlying mechanism by which extreme local stresses can trigger dislocation character transformation in low-SFE TRIP steels.\u003c/p\u003e"},{"header":"4. Conclusions","content":"\u003cp\u003eIn this study, the deformation behavior of a high-Mn TRIP steel was investigated by in-situ straining transmission electron microscopy, with particular focus on the dynamic role of stacking-fault (SF) intersections during plastic deformation. The main findings are summarized as follows:\u003c/p\u003e \u003cp\u003e \u003col\u003e \u003cspan\u003e \u003cli\u003e \u003cp\u003ePlastic deformation is dominated by Shockley partial dislocations due to the low stacking-fault energy of the alloy, leading to extensive stacking-fault formation on multiple {111} planes and the development of a three-dimensional network of intersecting faults.\u003c/p\u003e \u003c/li\u003e \u003c/span\u003e \u003cspan\u003e \u003cli\u003e \u003cp\u003eStacking faults formed on different {111} planes frequently intersect within grain interiors. Real-time TEM observations directly confirm that these intersections act as strong deformation-generated barriers to partial dislocation motion. The resulting dislocation pile-up and local strain concentration contribute significantly to the pronounced work-hardening behavior of the TRIP steel.\u003c/p\u003e \u003c/li\u003e \u003c/span\u003e \u003cspan\u003e \u003cli\u003e \u003cp\u003eAlthough SF intersections primarily function as strengthening obstacles, localized and transient cross-slip events can occur under sufficiently high local stress conditions. These events are initiated by stress-assisted recombination of leading and trailing partial dislocations into a perfect dislocation segment, followed by rotation of the dislocation line into screw character (\u003cb\u003eu\u003c/b\u003e ∥ \u003cb\u003eb\u003c/b\u003e), which enables cross-slip onto an alternative {111} plane.\u003c/p\u003e \u003c/li\u003e \u003c/span\u003e \u003cspan\u003e \u003cli\u003e \u003cp\u003eThe observed cross-slip does not reflect intrinsically facile partial dislocation motion in low-SFE alloys. Rather, it represents a stress-activated dislocation character transformation that occurs only after substantial stress accumulation at SF intersections.\u003c/p\u003e \u003c/li\u003e \u003c/span\u003e \u003c/ol\u003e \u003c/p\u003e \u003cp\u003eOverall, the present in-situ observations demonstrate that stacking-fault intersections in TRIP steel exhibit a dual but asymmetric mechanical role: they primarily enhance strength by blocking partial dislocation glide, while secondarily providing a localized, stress-driven pathway for dislocation reconfiguration. These findings refine the mechanistic understanding of intersection-controlled plasticity and highlight the dynamic nature of dislocation processes in low-SFE austenitic steels.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAcknowledgments\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis work was supported by a Research Grant of Pukyong National University(2025).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthors\u0026apos; contributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eS.D. Kim conceived the study, designed the experiments, performed the in-situ TEM experiments, analyzed the data, and wrote the manuscript. The author read and approved the final manuscript.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting interests\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe author declares that he has no competing interests.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis work was supported by a Research Grant of Pukyong National University (2025).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAvailability of data and materials\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe datasets generated during the current study are available from the corresponding author on reasonable request.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eO. Gr\u0026auml;ssel, L. Kr\u0026uuml;ger, G. Frommeyer, and L.W. Meyer, High strength Fe\u0026ndash;Mn\u0026ndash;(Al, Si) TRIP/TWIP steels development\u0026mdash;properties and applications, \u003cem\u003eInt. J. Plasticity\u003c/em\u003e \u003cstrong\u003e16\u003c/strong\u003e, 1391\u0026ndash;1409 (2000).\u003c/li\u003e\n\u003cli\u003eK.T. Park, K.G. Jin, S.H. Han, S.W. Hwang, and C.S. Lee, Stacking fault energy and plastic deformation of fully austenitic high manganese steels: Effect of Al addition, \u003cem\u003eMater. Sci. Eng. A\u003c/em\u003e \u003cstrong\u003e527\u003c/strong\u003e, 3651\u0026ndash;3658 (2010).\u003c/li\u003e\n\u003cli\u003eD.T. Pierce, D. Raabe, J.A. Jim\u0026eacute;nez, J. Bentley, and J.E. Wittig, The influence of manganese content on the stacking fault and austenite/\u0026epsilon;-martensite interfacial energies in Fe\u0026ndash;Mn steels, \u003cem\u003eActa Mater.\u003c/em\u003e \u003cstrong\u003e68\u003c/strong\u003e, 238\u0026ndash;253 (2014).\u003c/li\u003e\n\u003cli\u003eI. Gutierrez-Urrutia and D. Raabe, Dislocation and twin substructure evolution during strain hardening of an Fe\u0026ndash;22Mn\u0026ndash;0.6C TWIP steel, \u003cem\u003eActa Mater.\u003c/em\u003e \u003cstrong\u003e60\u003c/strong\u003e, 5791\u0026ndash;5802 (2012).\u003c/li\u003e\n\u003cli\u003eT.S. Byun, On the stress dependence of partial dislocation separation and deformation twinning in FCC metals, \u003cem\u003eActa Mater.\u003c/em\u003e \u003cstrong\u003e51\u003c/strong\u003e, 3063\u0026ndash;3071 (2003).\u003c/li\u003e\n\u003cli\u003eS. Allain, J.P. Chateau, O. Bouaziz, S. Migot, and N. Guelton, Correlations between the calculated stacking fault energy and the plasticity mechanisms in Fe\u0026ndash;Mn\u0026ndash;C alloys, \u003cem\u003eMater. Sci. Eng. A\u003c/em\u003e \u003cstrong\u003e387\u0026ndash;389\u003c/strong\u003e, 158\u0026ndash;162 (2004). \u003c/li\u003e\n\u003cli\u003eH.K. Kim, S.H. Kim, and J.P. Ahn, Methods to evaluate the twin formation energy: comparative studies of atomic simulations and in-situ TEM tensile tests, \u003cem\u003eAppl. Microsc.\u003c/em\u003e \u003cstrong\u003e50\u003c/strong\u003e, 19 (2020). https://doi.org/10.1186/s42649-020-00039-2\u003c/li\u003e\n\u003cli\u003eB.C. De Cooman, Y. Estrin, and S.K. Kim, Twinning-induced plasticity (TWIP) steels, \u003cem\u003eActa Mater.\u003c/em\u003e \u003cstrong\u003e142\u003c/strong\u003e, 283\u0026ndash;362 (2018). \u003c/li\u003e\n\u003cli\u003eKo, K.K., Jang, J.H., Tiwari, S. \u003cem\u003eet al.\u003c/em\u003e Quantitative analysis of retained austenite in Nb added Fe-based alloy. \u003cem\u003eAppl. Microsc.\u003c/em\u003e \u003cstrong\u003e52\u003c/strong\u003e, 5 (2022). https://doi.org/10.1186/s42649-022-00074-1 \u003c/li\u003e\n\u003cli\u003eH. Idrissi, K. Renard, L. Ryelandt, D. Schryvers, and P.J. Jacques, On the mechanism of twin formation in Fe\u0026ndash;Mn\u0026ndash;C TWIP steels, \u003cem\u003eActa Mater.\u003c/em\u003e \u003cstrong\u003e58\u003c/strong\u003e, 2464-2476 (2010).\u003c/li\u003e\n\u003cli\u003eM. Koyama, T. Sawaguchi, T. Lee, C.S. Lee, and K. Tsuzaki, Work hardening associated with martensitic transformation, twinning, and dislocation glide in metastable austenitic steels, \u003cem\u003eMater. Sci. Eng. A\u003c/em\u003e \u003cstrong\u003e528\u003c/strong\u003e, 7310\u0026ndash;7316 (2011).\u003c/li\u003e\n\u003cli\u003eJ. Talonen and H. H\u0026auml;nninen, Formation of shear bands and strain-induced martensite during plastic deformation of metastable austenitic stainless steel, \u003cem\u003eActa Mater.\u003c/em\u003e \u003cstrong\u003e55\u003c/strong\u003e, 6108\u0026ndash;6118 (2007).\u003c/li\u003e\n\u003cli\u003eD. Hull and D.J. Bacon, \u003cem\u003eIntroduction to Dislocations\u003c/em\u003e, 5th ed., Butterworth-Heinemann, Oxford (2011).\u003c/li\u003e\n\u003cli\u003eA. Dumay, J.P. Chateau, S. Allain, S. Migot, and O. Bouaziz, Influence of addition elements on the stacking fault energy and mechanical properties of an austenitic Fe\u0026ndash;Mn\u0026ndash;C steel, \u003cem\u003eMater. Sci. Eng. A\u003c/em\u003e \u003cstrong\u003e483\u0026ndash;484\u003c/strong\u003e, 184\u0026ndash;187 (2008).\u003c/li\u003e\n\u003cli\u003eJ.P. Hirth and J. Lothe, \u003cem\u003eTheory of Dislocations\u003c/em\u003e, 2nd ed., Wiley, New York (1982).\u003c/li\u003e\n\u003cli\u003eS.J. Pennycook and P.D. Nellist, \u003cem\u003eScanning Transmission Electron Microscopy: Imaging and Analysis\u003c/em\u003e, Springer, New York (2011).\u003c/li\u003e\n\u003cli\u003eP.E. Batson, N. Dellby, and O.L. Krivanek, Sub-angstrom resolution using aberration corrected electron optics, \u003cem\u003eNature\u003c/em\u003e \u003cstrong\u003e418\u003c/strong\u003e, 617\u0026ndash;620 (2002).\u003c/li\u003e\n\u003cli\u003eJ.K. Kim, Y. Estrin, and B.C. De Cooman, Constitutive modeling of the stacking fault energy-dependent deformation behavior of Fe\u0026ndash;Mn\u0026ndash;C TWIP steels, \u003cem\u003eMetall. Mater. Trans. A\u003c/em\u003e \u003cstrong\u003e49\u003c/strong\u003e, 5919\u0026ndash;5924 (2018).\u003c/li\u003e\n\u003cli\u003eZ. Li, Y. Zhao, and J. Li, The influence of stacking faults on mechanical behavior of advanced materials: A review, \u003cem\u003eMater. Sci. Eng. A\u003c/em\u003e \u003cstrong\u003e789\u003c/strong\u003e, 139660 (2020).\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":true,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"applied-microscopy","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"appm","sideBox":"Learn more about [Applied Microscopy](http://appmicro.springeropen.com)","snPcode":"","submissionUrl":"https://www.editorialmanager.com/APPM/default.aspx","title":"Applied Microscopy","twitterHandle":"@SpringerOpen","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"BMC/SO AJ","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"High-manganese TRIP steel, In-situ TEM, Stacking fault interaction, Partial dislocation, Work hardening","lastPublishedDoi":"10.21203/rs.3.rs-9026817/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-9026817/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThe deformation behavior of a high-manganese transformation-induced plasticity (TRIP) steel was investigated using in-situ straining transmission electron microscopy (TEM), with emphasis on the dynamic interaction between stacking faults and partial dislocations during plastic deformation. Owing to the low stacking-fault energy of the alloy, plastic deformation is dominated by Shockley partial dislocations, leading to extensive stacking-fault formation on multiple {111} planes. As deformation proceeds, stacking faults generated on different slip variants frequently intersect within grain interiors. Real-time observations demonstrate that these intersections act as strong deformation-generated barriers that impede partial dislocation motion. The resulting dislocation pile-up and local strain concentration contribute significantly to the pronounced work-hardening capability of the TRIP steel. Despite this strong blocking effect, detailed in-situ analysis reveals that stacking-fault intersections are not strictly impenetrable. Under conditions of significant dislocation accumulation, the separation distance between leading and trailing partial dislocations can locally decrease, allowing their temporary recombination into a perfect dislocation segment. The recombined dislocation assumes screw character, which enables cross-slip onto a secondary {111} slip plane. After cross-slip, the perfect dislocation can redissociate into Shockley partial dislocations due to the low stacking-fault energy of the alloy, allowing glide to resume on the new slip plane. These observations demonstrate that stacking-fault intersections primarily function as strengthening barriers to partial dislocation motion, while occasionally enabling stress-assisted dislocation recombination and localized cross-slip. The present in-situ TEM results provide direct mechanistic insight into the dynamic interaction between stacking faults and dislocations and clarify how stacking-fault intersections influence both strain hardening and local plastic accommodation in high-Mn TRIP steels.\u003c/p\u003e","manuscriptTitle":"In-situ TEM Investigation of Stacking-Fault Intersection–Controlled Deformation in High-Mn TRIP Steel","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-03-11 18:52:58","doi":"10.21203/rs.3.rs-9026817/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Major revision","date":"2026-03-23T23:58:23+00:00","index":"","fulltext":""},{"type":"reviewerAgreed","content":"","date":"2026-03-08T06:15:38+00:00","index":0,"fulltext":""},{"type":"reviewersInvited","content":"","date":"2026-03-06T02:09:01+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"Applied Microscopy","date":"2026-03-06T01:58:29+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2026-03-06T01:24:16+00:00","index":"","fulltext":""},{"type":"submitted","content":"Applied Microscopy","date":"2026-03-04T02:07:14+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"applied-microscopy","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"appm","sideBox":"Learn more about [Applied Microscopy](http://appmicro.springeropen.com)","snPcode":"","submissionUrl":"https://www.editorialmanager.com/APPM/default.aspx","title":"Applied Microscopy","twitterHandle":"@SpringerOpen","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"BMC/SO AJ","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"f5c7568f-8de9-434e-8af2-3ebcac9d836f","owner":[],"postedDate":"March 11th, 2026","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[],"tags":[],"updatedAt":"2026-04-23T09:13:30+00:00","versionOfRecord":[],"versionCreatedAt":"2026-03-11 18:52:58","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-9026817","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-9026817","identity":"rs-9026817","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}