Effect of phosphorus content on the microstructure evolution of highly undercooled Al-60%Si alloys

Effect of phosphorus content on the microstructure evolution of highly undercooled Al-60%Si alloys | 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 Effect of phosphorus content on the microstructure evolution of highly undercooled Al-60%Si alloys Bo Dang, Zengyun Jian, Junfeng Xu This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-4877813/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 08 Jan, 2025 Read the published version in Silicon → Version 1 posted 9 You are reading this latest preprint version Abstract In order to investigate the effect of P content on the growth morphology and the growth mode of Si phase, the Al-60%Si alloys with 0.5%P and 1.0%P was subjected to deep undercooling by electromagnetic levitator. The morphology evolution and growth mode of Si phase was studied by analyzing the dynamic images recorded by HSV and the SEM images of as-solidified samples. The results reveal that the morphology of Si phase changed from the large strip shape to coarse bulks and regularly arranged dendrites, then to spheroidal and rod-shaped with increasing of undercooling, and the corresponding growth mode changed from lateral growth to mixed growth, then to continuous growth. The P refines the size of the Si phase by increasing the nucleation rate of Si phase. With rising of P content, the critical undercoolings of growth mode transition decrease, and the experimental results well match the theoretical predicted results. Al-Si alloys Highly undercooled Morphology evolution Critical undercooling Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 1. Introduction Hypereutectic Al-Si alloy has been widely used in aerospace, machine manufacture, automobile, ships, chemical and other industry for its excellent comprehensive properties, such as low density, low thermal expansion coefficient, high strength, stable size, good corrosion resistance and wear resistance [ 1 – 3 ]. However, the coarse long strip primary Si and acicular eutectic Si in the microstructure of hypereutectic Al-Si alloy generate stress concentration at the edges and corners which cracks the Al matrix and reduces the properties of the alloy [ 4 – 6 ]. In addition, the size of Si phase in hypereutectic Al-Si alloys rises markedly with the increase of Si content, which limits the application range of the alloys. Therefore, in order to satisfy the application requirements, the morphology and size of Si phase in hypereutectic Al-Si alloys must be modified. The refinement of Si phase size and morphology in the microstructure of hypereutectic Al-Si alloy is predominantly based on the principles of rising the nucleation sites in the liquid phase to increase the nucleation rate, reducing the growth rate of crystal nuclei or inhibit the growth of crystal nuclei, and regulating the temperature distribution at the crystallization front [ 7 – 10 ]. The common method is to increase the nucleation undercooling during solidification and add nucleating agents or modifiers such as second phase, refinement elements and alloying elements [ 8 , 9 ]. At present, the simple and convenient method is to add modification elements, among which the refining effect of phosphorus (P) is the most efficient. The modifier P is often added to the alloy in the form of elemental P, P comprising master alloys, phosphates and phosphorus compounds in the production process. Sterner-Rainer first discovered that P can refine the primary Si in hypereutectic Al-Si alloys [ 11 ]. Zhu XZ et al found the Al-3P modifier considerably raises the number density, and results in the size of primary Si in Al-18%Si alloy decreases from 160 µm to 28 µm with 0.04%P [ 12 ]. Zhou XL developed the novel modifier of Si-18Mn-16Ti-11P master alloy to refine the size of primary Si to 14.7 ± 1.3 µm, modify the morphology of primary Si to regular block, and homogenize the distribution of primary silicon in Al-27%Si alloy [ 13 ]. At present, a lot of research has a main focus on the microstructure and properties of cast P-modified Al-Si alloys. However, in order to regulate the microstructure and properties of the P-modified Al-Si alloy, it is required to understand the law of nucleation and growth of Si phase in the P-modified Al-Si alloy. Based on the characteristics of semiconductor materials, the solid Si can be differentiated from the highly undercooled Al-Si melt, and the entire solidification process can be recorded using a high-speed video (HSV) [ 14 – 16 ]. Xu et al [ 17 ] investigated the nucleation rate and growth rate of Si phase using the HSV images. Aoyama et al [ 18 ] believed the growth mode of Si has lateral growth, continuous growth, and continuous nucleation based on the morphology change of Si, and determined the undercooling transition were 100 and 210 K. Although there have been some studies on the solidification process of highly undercooled Al-Si alloys, the effect of P content on the morphology evolution and growth mode of Si phase of highly undercooled Al-Si alloys has rarely been studied. In this paper, the solidification process of highly undercooled Al-60%Si alloys with 0.5%P and 1.0%P have dynamically observed and recorded by HSV. The growth mode of Si phase was divided by analyzing the growth morphology of Si phase in HSV images and the as-solidified microstructure of scanning electron microscopy (SEM) images. On this basis, the critical undercoolings of the growth mode transition of Si phase were determined. 2. Experimental procedures The raw alloys used in the experiment are 99.99%Al, 99.999%Si and Cu-13%P master alloys melted in a vacuum arc furnace (the contents in this paper are all mass fractions). The vacuum arc furnace can be vacuumed to 10 − 3 Pa, and then filled with 99.999% purified argon gas. A titanium evaporator is applied to remove the residual oxygen before melting. In order to make the alloy composition uniform, the alloy is repeatedly inverted melting many times. The loss of alloy mass in the entire melting process does not exceed 2%. Divide the solidified ingots into about 0.25 g for highly undercooled experiments. Highly undercooled experiments were performed in an electromagnetic levitation (EML) facility, as described in our previous study [ 19 , 20 ]. The vacuum chamber can be vacuumed to 10 − 4 Pa with a molecular pump and then filled with argon with 99.999% purity. The samples is placed on the BN crucible located in the center of the electromagnetic coil which is coupled to a high frequency power. The alloy preheated by CO 2 laser located above the vacuum chamber, and then heated and levitated by high frequency power. The temperature of alloy was recorded by an infrared thermometer located on the side of the vacuum chamber (its operating spectrum is 1.6 µm and response time is 2 ms) and regulated by changing the laser power and high frequency power. The nucleation undercooling was achieved by regulating the flow rate of helium gas. The entire process of melting, levitation and solidification of the alloy is observed and recorded by a HSV located on the other side. The microstructure of the as-solidified alloy was observed by SEM. 3. Results and discussion 3.1 the solidification of undercooled Al-60%Si-0.5%P alloys Figure 1 displays the image recorded by a HSV during the solidification process of undercooled Al-60%Si-0.5%P alloys. In the images, the white part is solid Si phase, the black part is the undercooled liquid phase, and the solid-liquid interface is the edge of the Si phase. The t = 0 ms in the images is the solid Si phase first crystallized time. At a small undercooling of Δ T = 43 K, as displayed in Fig. 1 (a), the Si phase nucleates from a certain point of the undercooled melt, and then grows rapidly along the nucleation point in a certain direction and slowly in the corresponding vertical direction formed long and slender flake Si phase with the rising of solidification time. At last, the long flake Si phase with distinctly edges and angles interleaved with each other displaying a dendritic morphology, and the growth mode demonstrated obvious anisotropic growth. The growth morphology of Si phase was modified when the undercooling rises to Δ T = 95 K, as shown in Fig. 1 (b). Although the Si phase grows from the nucleation point with the same rate in all directions, The final surface of the alloys was coated with the lamellar Si phase with smooth edge and passivated corners and long flake Si phase with evident sharp corners. When the undercooling further rises to Δ T = 182 K, as shown in Figs. 1 (c), the growth rate of the Si phase visibly increased. The Si phase grows from the more nucleate sites in undercooled melt. The long flake Si phase growth has vanished, and the massive shapes Si phase with uneven edges cover the surface of the alloys. At the undercooling of Δ T = 209 K, as shown in Figs. 1 (d), the growth mode of Si phase modified again. The size of Si phase becomes very minor so that the high-speed camera could not differentiate it. The growth direction displayed isotropy, and it only took 8 ms for the growth process of the Si phase. In addition, it has long been considered that the solid-liquid interface is the recalescence interface, a large number of studies have been conducted on the crystal’s growth rate utilizing photodiodes and HSV [ 21 , 22 ]. However, it can be clearly seen that solid-liquid interface is not the recalescence interface in our research. At small undercooling, only solid-liquid interface and undercooled melt can be observed in the images, and the recalescence interface can not be differentiated due to the less crystallization latent heat. With rising of undercooling, the morphology of recalescence interface is a bumpy mountain shape, and the moving rate is faster than the rate of solid-liquid interface. When the undercooling is large sufficient, the solid-liquid interface and the recalescence interface move at same rate, and the morphology is a smooth and continuous shape. The surface morphology of the as-solidified sample was observed by SEM, the results displayed in Fig. 2 . When the undercooling of Δ T = 43 K, the morphology of Si phase is long strip shape with evident edges and angles. The significant twin grooves can be found in the microstructure, and the size of Si phase is about 1 mm, as shown in Fig. 2 (a). At small undercooling, the crystals preferentially grow on the close-packed surface during the growth process. The close-packed surface of Si crystals is {111} and its Jackson factor α = 2.71, which is a typical smooth interface and the growth mode is lateral growth mode [ 23 ]. In this case, atoms in the liquid phase are easy to attach to the step formed by defects such as dislocation and twins, and the growth depends on steps spreading out to their sides (parallel to the interface) which resulting in the crystal with a specific orientation and obvious twin boundaries (TPRE growth mechanism) [ 24 ]. As undercooling rises to Δ T = 95 K, the long strip shape Si phase with evident edges and angles still exists, and the dendrites with regular arrangement and smooth surface appear between the long strips shape Si phase which is characterized by continuous growth. The size of Si phase decreases to about 200 µm, as shown in Fig. 2 (b). At the undercooling of Δ T = 182 K, the long strip shape Si phase has entirely disappeared, and the morphology of Si phase changes to smooth spherical and short rod with obvious edges, as shown in Fig. 2 (c). When the undercooling rises to Δ T = 209 K, the morphology of Si phase is completely changed to spheroidal and rod-shaped with random distribution, and the size of Si phase is about 15 µm, as shown in Fig. 2 (d). The growth mode of Si phase has completely changed to continuous growth. The continuous growth corresponds to the microscopic rough interface, which is generally uneven on the atomic scale, and the liquid phase atoms can be deposited and grown at any position of the solid-liquid interface [ 25 ]. Thus, the growth of crystal has shown isotropy, and the morphology is smooth without edges and corners. Combining the images recorded by the HSV during the solidification process and the SEM images after solidification, it can be found that the growth morphology of Si phase in the Al-60%Si-0.5%P alloys change from the dendritic to massive, and then to short rod. The growth mode of Si phase changes from lateral growth to mixed growth with lateral and continuous growth, and then to continuous growth. The critical undercoolings of growth mode change are 86 K and 198 K, respectively. 3.2 the solidification of undercooled Al-60%Si-1.0%P alloys The growth morphology of Si phase for the undercooled Al-60%Si-1.0%P alloy is almost the same as that of the Al-60%Si-0.5%P alloy, as shown in Fig. 3 . At a small undercooling (Δ T = 42 K), the Si phase grows with a core in the melt and eventually grows as long strip shape with side-branching, as displayed in Fig. 3 (a). When the undercooling rises to Δ T = 83 K, the Si phase grows from the multiple nucleation points with all directions and grows as lamellar shape. At the later stage of solidification, Si grows in a certain direction from the edge of the strip Si or other nucleation points forming sharp corners, as shown in Fig. 3 (b). As the undercooling increases to Δ T = 155 K, the Si phase still grows as lamellar shape and no strip Si exists, as shown in Fig. 3 (c). The undercooling further increases to Δ T = 186 K, the Si phase nucleates continuously at the front of the solid-liquid interface, and the morphology of solid-liquid interface is smooth and continuous, as shown in Fig. 3 (d). The moving rate of solid-liquid interface considerably accelerated, and coated the all surface of the sample in only 8 ms. The nucleation and growth morphology of Si phase can not identified by the HSV because of the fine point morphology of Si phase. Figure 4 exhibits the SEM images of the surface morphology of as-solidified Al-60%-Si-1.0%P alloys. At small undercooling, the morphology of Si phase is coarse and long shapes with evident edges and angles, and the size of Si phase is about 500 µm, as shown in Fig. 4 (a). The typical twin grooves can be found in some areas, showing significant lateral growth characteristics. At moderate undercooling, the surface of the samples coated by long strips with edges and regular bulky Si, showing a mixed growth mode of lateral growth and continuous growth, as shown in Fig. 4 (b) and 4(c). At large undercooling, the Si phase is short rod-like and spheroidal with small size and smooth surface, exhibiting continuous growth, as shown in Fig. 4 (d). In general, the growth mode of Si phase in the undercooled Al-60%Si-1.0%P alloys change twice during solidification. The one is from lateral growth to mixed growth of lateral growth and continuous growth, and the other is from mixed growth to continuous growth. Combined with the HSV and SEM images, the critical undercooling for the two growth mode transitions are 50 K and 162 K, respectively. 3.3 The effect of P on the nucleation and growth of Al-60%Si alloys Si is a semiconductor material with a complex face-centered cubic structure similar to diamond. P reacts with liquid aluminum at approximately 1073 K to form AlP particles with high melting point after adding to Al-Si melt [ 26 ]. The atomic structure of AlP is the same as that of Si, and it is also a complex face-centered cubic structure similar to diamond [ 27 ]. P can filled in the tetrahedral gap, and each P atom is surrounded by four adjacent Al atoms during solidification. In addition, the lattice constant of AlP is a = 0.545 nm, while that of Si is 0.543nm [ 28 ]. According to the heterogeneous nucleation theory, AlP can act as the core of Si nuclei. When 0.5%P is added to the Al-Si alloy, a small number of AlP particles with high melting point are first formed in the melt during solidification, and the later Si particles are attached to the AlP particles to nucleate and grow. With the increase of P content to 1.0%, the more AlP particles can be formed in the melt which reduces the driving force and undercooling required for Si phase nucleation and growth. Figure 5 compares the microstructure evolution of undercooled Al-60%Si alloy with various P content at the undercooling of about 125 K. For Al-60%Si-0.5%P alloy, the Si phase is obviously refined with a size of about 100 µm, as shown in Fig. 5 (a). The Si phase of Al-60%Si-1.0%P alloy is further refined with a size of about 20 µm, as shown in Fig. 5 (b). It is found that the size of Si phase decreases significantly with the increase of P content, and the number of grains per unit volume increases significantly which indicates that P element can improve the nucleation rate of Si phase during solidification, and further refine the size of Si phase. 3.4 The effect of P on the critical undercooling for growth mode transition Since Li et al. [ 29 ] first applied electromagnetic levitation technology to study the growth morphology and growth mode of semiconductor Si, researchers have investigated a large number of experiments on Si, Ge and their alloys, and it is generally believed that the growth mode of Si will change twice during solidification. In this paper, it is found that the growth mode of Si phase for undercooled Al-60%Si alloy changes twice after adding P element. The first transition is from the lateral growth mode to the mixed growth mode of lateral growth and continuous growth, and the second transition is from mixed growth mode to continuous growth mode. Jian et al. [ 30 ] constructed a model using parameters such as melting point, thermodynamic equilibrium fraction and entropy of fusion, and theoretical predicted the critical undercooling for growth mode transformation. The critical undercoolings predicted theoretical for undercooled Al-60%Si alloys with various P content was shown in Fig. 6 , and found that the critical undercoolings decrease with the increase of P content. Compared with the theoretical predicted results and experimental results which are confirmed by HSV and SEM images, the difference is lower than 5% which indicated that the experimental results match well with the theoretical results. 4 Conclusion Al-60%Si-0.5%P and Al-60%Si-1.0%P alloys were highly undercooled by EML. The growth morphology of Si phase during solidification process was observed and recorded by HSV. The surface morphology of as-solidified alloys was analyzed by SEM. The results show that: The Si phase of both Al-60%Si-0.5%P and Al-60%Si-1.0%P alloys present large strip shapes at small undercooling, coarse bulks and regularly arranged dendrites at moderate undercooling, and spheroidal and rod-shaped at large undercooling. There are three growth modes of Si phase is lateral growth, mixed growth and continuous growth. P can obviously refine the size, morphology, distribution, critical undercoolings of growth mode transition of Si phase. P reacts with Al formed AlP particles, which promotes the nucleation rate of Si phase. The critical undercoolings of growth mode transition of Al-60%Si-0.5%P alloy are 86 and 198 K, respectively, and for Al-60%Si-1.0%P alloys are 50 and 162 K, which match well with the theoretical predicted results. Declarations Funding The work was supported by the Scientific Research Program Funded by Shaanxi Province Education Department (No. 23JK0484). Author Contribution Author 1 (B. D.): Investigation, Formal Analysis, Writing - Original Draft; Author 2 (Z.Y. J.): Conceptualization, Funding Acquisition, Supervision, Review & Editing; Author 3 (J.F. X.): Review & Editing. References Ding C, Hao HL, Lu ZG et al (2023) Fabrication of hypereutectic Al-Si alloy with improved mechanical and thermal properties by hot extrusion. Mater Charact 202:113026 Zhang XG, Chen JY, Zhan Y et al (2024) Interfacial characteristics of dual-phase Si/TiB 2 and its crack initiation mechanism in hypereutectic Al-Si alloys. J Alloy Compd 981:173748 Peng JF, Wang WL, Yuan SJ et al (2024) Improved mechanical and frictional properties of hypereutectic Al-Si alloy by modifying Si phase with La addition. Mater Today Commun 38:107857 Li CY, Liu F, Yu FX et al (2023) The growth mechanism and morphology evolution of primary Si during slow cooling solidification of high purity Al-15Si alloy with Cr additions. J Mater Res Technol 23:1204–1213 Yan PY, Mao WM, Fan J et al (2020) Microstructural evolution, segregation and fracture behavior of A390 alloy prepared by combined Rheo-HPDC processing and Sr-modifier. J Alloy Compd 835:155297 Li QL, Xia TD, Lan YF et al (2013) Effect of in situ γ-Al 2 O 3 particles on the microstructure of hypereutectic Al-20%Si alloy. J Alloy Compd 577:232–236 Todaro CJ, Easton MA, Qiu D et al (2019) Effect of ultrasonic melt treatment on intermetallic phase formation in a manganese-modified Al-17Si-2Fe alloy. J Mater Process Tech 271:346–356 Uzun O, Kilicaslan MF, Yılmaz F (2014) Formation of novel flower-like silicon phases and evaluation of mechanical properties of hypereutectic melt-spun Al-20Si-5Fe alloys with addition of V. Mat Sci Eng A 607:368–375 Li QL, Xia TD, Lan YF et al (2013) Effect of rare earth cerium addition on the microstructure and tensile properties of hypereutectic Al-20%Si alloy. J Alloy Compd 562:25–32 Lan Q, Cheng CL, Zhang JF et al (2019) The relationship between the thermoelectric power and resultant solidification microstructures of Al-Si melt under electromagnetic field. Mater Chem Phys 231:203–215 Sterner Rainer R Aluminium Silicon Alloy with a Phosphorus Content of 0.001 to 0.1%: US, 1940922[P], 26 Dec.,1933. Zhu XZ, Wang SH, Dong XX et al (2022) Morphologically templated nucleation of primary Si on AlP in hypereutectic Al-Si alloys. J Mater Res Technol 100:36–45 Zhou XL, Zhu XZ, Gao T et al (2016) Evolution of a novel Si-18Mn-16Ti-11P alloy in Al-Si melt and its influence on microstructure and properties of high-Si Al-Si alloy. Results Phys 6:737–745 Li D, Herlach DM (1996) Direct measurements of free crystal growth in deeply undercooled melts of semiconducting materials. Phys Rev Lett 77:1801–1804 Li DL, Mao XM, Fu HZ (1994) Electromagnetic levitation melting of solar grade silicon material. J Mater Sci Lett 13:1066–1068 Wang RY, Lu WH, Hogan LM (1999) Growth morphology of primary silicon in cast Al-Si alloys and the mechanism of concentric growth. J Cryst Growth 207:43–54 Xu JF, Diao L, Yan JH et al (2016) In situ observations of the rapid solidification for undercooled Al30Si70 alloy melt. J Mater Res 31:222–231 Aoyama T, Kuribayashi K (2001) Rapid solidification processes of semiconductors from highly undercooled melts. Mat Sci Eng A 304–306:231–234 Dang B, Jian ZY, Xu JF (2022) Effect of cerium-rich mischmetal content on the growth morphology and microstructure evolution of undercooled Al-70 wt%Si alloys. Vacuum 205:111427 Dang B, Jian ZY, Xu JF (2023) Effect of overheating treatment on morphological evolution of highly undercooled Al-70%Si-0.5%RE alloys. Mater Chem Phys 295:127173 Nagashio K, Okamoto H, Kuribayashi K et al (2005) Fragmentation of faceted dendrite in solidification of undercooled B-doped Si melts. Metall Mater Trans A 36:3407–3413 Aoyama T, Takamura Y, Kuribayashi T (1999) Dendrite growth processes of silicon and germanium from highly undercooled melts. Metall Mater Trans A 30:1333–1339 Boukellal AK, Elvalli AKS, Debierre JM (2019) Equilibrium and growth facetted shapes in isothermal solidification of silicon: 3D phase-field simulations. J Cryst Growth 522:37–44 Spacil I, Gehringer D, Holec D et al (2024) Elucidating effects of Eu and P on solidification and precipitation of Al-7Si-0.3Mg based alloys refined by Ta and TiB 2 . J Alloy Compd 978:173343 Xiao T, Lv GQ, Bao Y et al (2020) Electromagnetic separation of coarse Al-Si melts: The migration behavior of iron-rich phase and continuous growth of primary silicon. J Alloy Compd 819:153006 Zhang Q, Liu XF, Dai HS (2009) Re-formation of AlP compound in Al-Si melt. J Alloy Compd 480:376–381 Zhu XZ, Wang SH, Dong XX et al (2022) Morphologically templated nucleation of primary Si on AlP in hypereutectic Al-Si alloys. J Mater Res Technol 100:36–45 Zhang YR, Gao T, Zhu XZ et al (2015) Refining and nucleating behaviors of AlP on primary phase in Al-Ge and Al-Ge-Si alloys. Mater Charact 99:195–199 Li DL, Mao XM, Fu HZ (1994) Electromagnetic levitation melting of solar grade silcion material. J Mater Sci Let 13:1066 Jian ZY, Kuribayashi K, Jie WQ (2004) Critical undercoolings for the transition from the lateral to continuous growth in undercooled silicon and germanium. Acta Mater 52:3323–3333 Additional Declarations No competing interests reported. Cite Share Download PDF Status: Published Journal Publication published 08 Jan, 2025 Read the published version in Silicon → Version 1 posted Editorial decision: Revision requested 04 Nov, 2024 Reviews received at journal 23 Oct, 2024 Reviewers agreed at journal 23 Oct, 2024 Reviewers agreed at journal 14 Oct, 2024 Reviewers agreed at journal 07 Oct, 2024 Reviewers invited by journal 04 Sep, 2024 Editor assigned by journal 22 Aug, 2024 Submission checks completed at journal 22 Aug, 2024 First submitted to journal 07 Aug, 2024 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. 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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-4877813","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":356384307,"identity":"f767ab16-9a95-4ae1-b348-7d980612dcaa","order_by":0,"name":"Bo Dang","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA1UlEQVRIiWNgGAWjYDCCG4yNDz5USPCwsTcfOPDhB1FamJsNZ5yxkOPjOZZ4cGYPUVrY26R52yqM5SRyjA9zsBGhg+92Y5vkjDMSiW0SOR8OM/AwyPOLHcCvRfLOwWYLoF8S23jebjhcYMFgOHN2An4tBjcSG2+CbWHP3XB4Bg9DgsFtwloagH4BamHIeXCYh404LU0gLcZsHDkMxGkB+QUYyBJybDzHDICBLEHYL3y32x8Co7KOR769+fGHDz9s5PmlCWhBBxKkKR8Fo2AUjIJRgB0AAGgjTsZURnl5AAAAAElFTkSuQmCC","orcid":"","institution":"Xi'an Technological University","correspondingAuthor":true,"prefix":"","firstName":"Bo","middleName":"","lastName":"Dang","suffix":""},{"id":356384308,"identity":"4420ae9f-0938-48c5-85d5-5fc81210eee4","order_by":1,"name":"Zengyun Jian","email":"","orcid":"","institution":"Xi'an Technological University","correspondingAuthor":false,"prefix":"","firstName":"Zengyun","middleName":"","lastName":"Jian","suffix":""},{"id":356384309,"identity":"c8b2e6d7-d629-40bd-b53a-c75c3c3b7844","order_by":2,"name":"Junfeng Xu","email":"","orcid":"","institution":"Xi'an Technological University","correspondingAuthor":false,"prefix":"","firstName":"Junfeng","middleName":"","lastName":"Xu","suffix":""}],"badges":[],"createdAt":"2024-08-08 03:29:48","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-4877813/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-4877813/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1007/s12633-024-03219-x","type":"published","date":"2025-01-08T15:57:36+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":66660597,"identity":"ce6018a9-67fd-4a81-9463-c762149ae625","added_by":"auto","created_at":"2024-10-15 08:49:37","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":3699475,"visible":true,"origin":"","legend":"\u003cp\u003eGrowth morphologies of Si phase of highly undercooled Al-60%Si-0.5%P alloys at various undercoolings: (a) 43 K; (b) 95 K; (c) 182 K; (d) 209 K\u003c/p\u003e","description":"","filename":"floatimage142.png","url":"https://assets-eu.researchsquare.com/files/rs-4877813/v1/73559c50240d5a4b3c2cdd20.png"},{"id":66660098,"identity":"2729ed26-8262-4287-9408-e0651570b968","added_by":"auto","created_at":"2024-10-15 08:41:37","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":1405563,"visible":true,"origin":"","legend":"\u003cp\u003eMicrostructure of highly undercooled Al-60%Si-0.5%P alloys at various undercoolings: (a) 43 K; (b) 95 K; (c) 182 K; (d) 209 K\u003c/p\u003e","description":"","filename":"floatimage233.png","url":"https://assets-eu.researchsquare.com/files/rs-4877813/v1/45c238a72a54777b59faed0c.png"},{"id":66662138,"identity":"feee6045-9977-4eef-9481-35d582d31a05","added_by":"auto","created_at":"2024-10-15 08:57:37","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":3787628,"visible":true,"origin":"","legend":"\u003cp\u003eGrowth morphologies of Si phase of highly undercooled Al-60%Si-1.0%P alloys at various undercoolings: (a) 42 K; (b) 83 K; (c) 155 K; (d) 186 K\u003c/p\u003e","description":"","filename":"floatimage323.png","url":"https://assets-eu.researchsquare.com/files/rs-4877813/v1/1abdac854f2f1a104452d2bb.png"},{"id":66660099,"identity":"95a1bebb-2c63-45db-a023-04680d139876","added_by":"auto","created_at":"2024-10-15 08:41:37","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":1708195,"visible":true,"origin":"","legend":"\u003cp\u003eMicrostructure of highly undercooled Al-60%Si-1.0%P alloys at various undercoolings: (a) 42 K; (b) 83 K; (c) 155 K; (d) 186 K\u003c/p\u003e","description":"","filename":"floatimage419.png","url":"https://assets-eu.researchsquare.com/files/rs-4877813/v1/c9a70cda351063817819c53c.png"},{"id":66660595,"identity":"c79e4d89-5523-48c6-8614-b32f8ccaf19a","added_by":"auto","created_at":"2024-10-15 08:49:37","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":706935,"visible":true,"origin":"","legend":"\u003cp\u003eThe effect of P on the microstructure of Al-60%Si alloys: (a) 0.5%P, Δ\u003cem\u003eT\u003c/em\u003e=126 K; (b) 1.0%P, Δ\u003cem\u003eT\u003c/em\u003e=123 K\u003c/p\u003e","description":"","filename":"floatimage515.png","url":"https://assets-eu.researchsquare.com/files/rs-4877813/v1/ac2cfb71c850227c05361b68.png"},{"id":66660594,"identity":"cfa452e9-d9b3-4b6b-b6aa-8efc3b4aaa11","added_by":"auto","created_at":"2024-10-15 08:49:37","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":113605,"visible":true,"origin":"","legend":"\u003cp\u003eThe effect of P content on critical undercooling of Al-60%Si alloys\u003c/p\u003e","description":"","filename":"Onlinefloatimage64.png","url":"https://assets-eu.researchsquare.com/files/rs-4877813/v1/67680bba8ad6a8e8b00e1011.png"},{"id":73693969,"identity":"71c05f25-93ee-44d0-8bba-e0ebef808e69","added_by":"auto","created_at":"2025-01-13 16:10:07","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":13455514,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-4877813/v1/e4e19a97-624b-45fa-9807-bd742e0f0819.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Effect of phosphorus content on the microstructure evolution of highly undercooled Al-60%Si alloys","fulltext":[{"header":"1. Introduction","content":" \u003cp\u003eHypereutectic Al-Si alloy has been widely used in aerospace, machine manufacture, automobile, ships, chemical and other industry for its excellent comprehensive properties, such as low density, low thermal expansion coefficient, high strength, stable size, good corrosion resistance and wear resistance [\u003cspan additionalcitationids=\"CR2\" citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]. However, the coarse long strip primary Si and acicular eutectic Si in the microstructure of hypereutectic Al-Si alloy generate stress concentration at the edges and corners which cracks the Al matrix and reduces the properties of the alloy [\u003cspan additionalcitationids=\"CR5\" citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]. In addition, the size of Si phase in hypereutectic Al-Si alloys rises markedly with the increase of Si content, which limits the application range of the alloys. Therefore, in order to satisfy the application requirements, the morphology and size of Si phase in hypereutectic Al-Si alloys must be modified.\u003c/p\u003e \u003cp\u003eThe refinement of Si phase size and morphology in the microstructure of hypereutectic Al-Si alloy is predominantly based on the principles of rising the nucleation sites in the liquid phase to increase the nucleation rate, reducing the growth rate of crystal nuclei or inhibit the growth of crystal nuclei, and regulating the temperature distribution at the crystallization front [\u003cspan additionalcitationids=\"CR8 CR9\" citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]. The common method is to increase the nucleation undercooling during solidification and add nucleating agents or modifiers such as second phase, refinement elements and alloying elements [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e, \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]. At present, the simple and convenient method is to add modification elements, among which the refining effect of phosphorus (P) is the most efficient. The modifier P is often added to the alloy in the form of elemental P, P comprising master alloys, phosphates and phosphorus compounds in the production process. Sterner-Rainer first discovered that P can refine the primary Si in hypereutectic Al-Si alloys [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]. Zhu XZ et al found the Al-3P modifier considerably raises the number density, and results in the size of primary Si in Al-18%Si alloy decreases from 160 \u0026micro;m to 28 \u0026micro;m with 0.04%P [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]. Zhou XL developed the novel modifier of Si-18Mn-16Ti-11P master alloy to refine the size of primary Si to 14.7\u0026thinsp;\u0026plusmn;\u0026thinsp;1.3 \u0026micro;m, modify the morphology of primary Si to regular block, and homogenize the distribution of primary silicon in Al-27%Si alloy [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eAt present, a lot of research has a main focus on the microstructure and properties of cast P-modified Al-Si alloys. However, in order to regulate the microstructure and properties of the P-modified Al-Si alloy, it is required to understand the law of nucleation and growth of Si phase in the P-modified Al-Si alloy. Based on the characteristics of semiconductor materials, the solid Si can be differentiated from the highly undercooled Al-Si melt, and the entire solidification process can be recorded using a high-speed video (HSV) [\u003cspan additionalcitationids=\"CR15\" citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e]. Xu et al [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e] investigated the nucleation rate and growth rate of Si phase using the HSV images. Aoyama et al [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e] believed the growth mode of Si has lateral growth, continuous growth, and continuous nucleation based on the morphology change of Si, and determined the undercooling transition were 100 and 210 K.\u003c/p\u003e \u003cp\u003eAlthough there have been some studies on the solidification process of highly undercooled Al-Si alloys, the effect of P content on the morphology evolution and growth mode of Si phase of highly undercooled Al-Si alloys has rarely been studied. In this paper, the solidification process of highly undercooled Al-60%Si alloys with 0.5%P and 1.0%P have dynamically observed and recorded by HSV. The growth mode of Si phase was divided by analyzing the growth morphology of Si phase in HSV images and the as-solidified microstructure of scanning electron microscopy (SEM) images. On this basis, the critical undercoolings of the growth mode transition of Si phase were determined.\u003c/p\u003e "},{"header":"2. Experimental procedures","content":" \u003cp\u003eThe raw alloys used in the experiment are 99.99%Al, 99.999%Si and Cu-13%P master alloys melted in a vacuum arc furnace (the contents in this paper are all mass fractions). The vacuum arc furnace can be vacuumed to 10\u003csup\u003e\u0026minus;\u0026thinsp;3\u003c/sup\u003e Pa, and then filled with 99.999% purified argon gas. A titanium evaporator is applied to remove the residual oxygen before melting. In order to make the alloy composition uniform, the alloy is repeatedly inverted melting many times. The loss of alloy mass in the entire melting process does not exceed 2%. Divide the solidified ingots into about 0.25 g for highly undercooled experiments.\u003c/p\u003e\u003cp\u003eHighly undercooled experiments were performed in an electromagnetic levitation (EML) facility, as described in our previous study [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e, \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e]. The vacuum chamber can be vacuumed to 10\u003csup\u003e\u0026minus;\u0026thinsp;4\u003c/sup\u003e Pa with a molecular pump and then filled with argon with 99.999% purity. The samples is placed on the BN crucible located in the center of the electromagnetic coil which is coupled to a high frequency power. The alloy preheated by CO\u003csub\u003e2\u003c/sub\u003e laser located above the vacuum chamber, and then heated and levitated by high frequency power. The temperature of alloy was recorded by an infrared thermometer located on the side of the vacuum chamber (its operating spectrum is 1.6 \u0026micro;m and response time is 2 ms) and regulated by changing the laser power and high frequency power. The nucleation undercooling was achieved by regulating the flow rate of helium gas. The entire process of melting, levitation and solidification of the alloy is observed and recorded by a HSV located on the other side. The microstructure of the as-solidified alloy was observed by SEM.\u003c/p\u003e "},{"header":"3. Results and discussion","content":"\u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003e3.1 the solidification of undercooled Al-60%Si-0.5%P alloys\u003c/h2\u003e \u003cp\u003eFigure \u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e displays the image recorded by a HSV during the solidification process of undercooled Al-60%Si-0.5%P alloys. In the images, the white part is solid Si phase, the black part is the undercooled liquid phase, and the solid-liquid interface is the edge of the Si phase. The \u003cem\u003et\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0 ms in the images is the solid Si phase first crystallized time.\u003c/p\u003e \u003cp\u003eAt a small undercooling of Δ\u003cem\u003eT\u003c/em\u003e\u0026thinsp;=\u0026thinsp;43 K, as displayed in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e(a), the Si phase nucleates from a certain point of the undercooled melt, and then grows rapidly along the nucleation point in a certain direction and slowly in the corresponding vertical direction formed long and slender flake Si phase with the rising of solidification time. At last, the long flake Si phase with distinctly edges and angles interleaved with each other displaying a dendritic morphology, and the growth mode demonstrated obvious anisotropic growth.\u003c/p\u003e \u003cp\u003eThe growth morphology of Si phase was modified when the undercooling rises to Δ\u003cem\u003eT\u003c/em\u003e\u0026thinsp;=\u0026thinsp;95 K, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e(b). Although the Si phase grows from the nucleation point with the same rate in all directions, The final surface of the alloys was coated with the lamellar Si phase with smooth edge and passivated corners and long flake Si phase with evident sharp corners.\u003c/p\u003e \u003cp\u003eWhen the undercooling further rises to Δ\u003cem\u003eT\u003c/em\u003e\u0026thinsp;=\u0026thinsp;182 K, as shown in Figs.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e(c), the growth rate of the Si phase visibly increased. The Si phase grows from the more nucleate sites in undercooled melt. The long flake Si phase growth has vanished, and the massive shapes Si phase with uneven edges cover the surface of the alloys.\u003c/p\u003e \u003cp\u003eAt the undercooling of Δ\u003cem\u003eT\u003c/em\u003e\u0026thinsp;=\u0026thinsp;209 K, as shown in Figs.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e(d), the growth mode of Si phase modified again. The size of Si phase becomes very minor so that the high-speed camera could not differentiate it. The growth direction displayed isotropy, and it only took 8 ms for the growth process of the Si phase.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eIn addition, it has long been considered that the solid-liquid interface is the recalescence interface, a large number of studies have been conducted on the crystal\u0026rsquo;s growth rate utilizing photodiodes and HSV [\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e, \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e]. However, it can be clearly seen that solid-liquid interface is not the recalescence interface in our research. At small undercooling, only solid-liquid interface and undercooled melt can be observed in the images, and the recalescence interface can not be differentiated due to the less crystallization latent heat. With rising of undercooling, the morphology of recalescence interface is a bumpy mountain shape, and the moving rate is faster than the rate of solid-liquid interface. When the undercooling is large sufficient, the solid-liquid interface and the recalescence interface move at same rate, and the morphology is a smooth and continuous shape.\u003c/p\u003e \u003cp\u003eThe surface morphology of the as-solidified sample was observed by SEM, the results displayed in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e. When the undercooling of Δ\u003cem\u003eT\u003c/em\u003e\u0026thinsp;=\u0026thinsp;43 K, the morphology of Si phase is long strip shape with evident edges and angles. The significant twin grooves can be found in the microstructure, and the size of Si phase is about 1 mm, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e(a). At small undercooling, the crystals preferentially grow on the close-packed surface during the growth process. The close-packed surface of Si crystals is {111} and its Jackson factor α\u0026thinsp;=\u0026thinsp;2.71, which is a typical smooth interface and the growth mode is lateral growth mode [\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e]. In this case, atoms in the liquid phase are easy to attach to the step formed by defects such as dislocation and twins, and the growth depends on steps spreading out to their sides (parallel to the interface) which resulting in the crystal with a specific orientation and obvious twin boundaries (TPRE growth mechanism) [\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eAs undercooling rises to Δ\u003cem\u003eT\u003c/em\u003e\u0026thinsp;=\u0026thinsp;95 K, the long strip shape Si phase with evident edges and angles still exists, and the dendrites with regular arrangement and smooth surface appear between the long strips shape Si phase which is characterized by continuous growth. The size of Si phase decreases to about 200 \u0026micro;m, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e(b). At the undercooling of Δ\u003cem\u003eT\u003c/em\u003e\u0026thinsp;=\u0026thinsp;182 K, the long strip shape Si phase has entirely disappeared, and the morphology of Si phase changes to smooth spherical and short rod with obvious edges, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e(c).\u003c/p\u003e \u003cp\u003eWhen the undercooling rises to Δ\u003cem\u003eT\u003c/em\u003e\u0026thinsp;=\u0026thinsp;209 K, the morphology of Si phase is completely changed to spheroidal and rod-shaped with random distribution, and the size of Si phase is about 15 \u0026micro;m, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e(d). The growth mode of Si phase has completely changed to continuous growth. The continuous growth corresponds to the microscopic rough interface, which is generally uneven on the atomic scale, and the liquid phase atoms can be deposited and grown at any position of the solid-liquid interface [\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e]. Thus, the growth of crystal has shown isotropy, and the morphology is smooth without edges and corners.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eCombining the images recorded by the HSV during the solidification process and the SEM images after solidification, it can be found that the growth morphology of Si phase in the Al-60%Si-0.5%P alloys change from the dendritic to massive, and then to short rod. The growth mode of Si phase changes from lateral growth to mixed growth with lateral and continuous growth, and then to continuous growth. The critical undercoolings of growth mode change are 86 K and 198 K, respectively.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003e3.2 the solidification of undercooled Al-60%Si-1.0%P alloys\u003c/h2\u003e \u003cp\u003eThe growth morphology of Si phase for the undercooled Al-60%Si-1.0%P alloy is almost the same as that of the Al-60%Si-0.5%P alloy, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e. At a small undercooling (Δ\u003cem\u003eT\u003c/em\u003e\u0026thinsp;=\u0026thinsp;42 K), the Si phase grows with a core in the melt and eventually grows as long strip shape with side-branching, as displayed in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e(a). When the undercooling rises to Δ\u003cem\u003eT\u003c/em\u003e\u0026thinsp;=\u0026thinsp;83 K, the Si phase grows from the multiple nucleation points with all directions and grows as lamellar shape. At the later stage of solidification, Si grows in a certain direction from the edge of the strip Si or other nucleation points forming sharp corners, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e(b). As the undercooling increases to Δ\u003cem\u003eT\u003c/em\u003e\u0026thinsp;=\u0026thinsp;155 K, the Si phase still grows as lamellar shape and no strip Si exists, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e(c). The undercooling further increases to Δ\u003cem\u003eT\u003c/em\u003e\u0026thinsp;=\u0026thinsp;186 K, the Si phase nucleates continuously at the front of the solid-liquid interface, and the morphology of solid-liquid interface is smooth and continuous, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e(d). The moving rate of solid-liquid interface considerably accelerated, and coated the all surface of the sample in only 8 ms. The nucleation and growth morphology of Si phase can not identified by the HSV because of the fine point morphology of Si phase.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e exhibits the SEM images of the surface morphology of as-solidified Al-60%-Si-1.0%P alloys. At small undercooling, the morphology of Si phase is coarse and long shapes with evident edges and angles, and the size of Si phase is about 500 \u0026micro;m, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e(a). The typical twin grooves can be found in some areas, showing significant lateral growth characteristics. At moderate undercooling, the surface of the samples coated by long strips with edges and regular bulky Si, showing a mixed growth mode of lateral growth and continuous growth, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e(b) and 4(c). At large undercooling, the Si phase is short rod-like and spheroidal with small size and smooth surface, exhibiting continuous growth, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e(d).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eIn general, the growth mode of Si phase in the undercooled Al-60%Si-1.0%P alloys change twice during solidification. The one is from lateral growth to mixed growth of lateral growth and continuous growth, and the other is from mixed growth to continuous growth. Combined with the HSV and SEM images, the critical undercooling for the two growth mode transitions are 50 K and 162 K, respectively.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003e3.3 The effect of P on the nucleation and growth of Al-60%Si alloys\u003c/h2\u003e \u003cp\u003eSi is a semiconductor material with a complex face-centered cubic structure similar to diamond. P reacts with liquid aluminum at approximately 1073 K to form AlP particles with high melting point after adding to Al-Si melt [\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e]. The atomic structure of AlP is the same as that of Si, and it is also a complex face-centered cubic structure similar to diamond [\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e]. P can filled in the tetrahedral gap, and each P atom is surrounded by four adjacent Al atoms during solidification. In addition, the lattice constant of AlP is \u003cem\u003ea\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.545 nm, while that of Si is 0.543nm [\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e]. According to the heterogeneous nucleation theory, AlP can act as the core of Si nuclei. When 0.5%P is added to the Al-Si alloy, a small number of AlP particles with high melting point are first formed in the melt during solidification, and the later Si particles are attached to the AlP particles to nucleate and grow. With the increase of P content to 1.0%, the more AlP particles can be formed in the melt which reduces the driving force and undercooling required for Si phase nucleation and growth.\u003c/p\u003e \u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e compares the microstructure evolution of undercooled Al-60%Si alloy with various P content at the undercooling of about 125 K. For Al-60%Si-0.5%P alloy, the Si phase is obviously refined with a size of about 100 \u0026micro;m, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e(a). The Si phase of Al-60%Si-1.0%P alloy is further refined with a size of about 20 \u0026micro;m, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e(b). It is found that the size of Si phase decreases significantly with the increase of P content, and the number of grains per unit volume increases significantly which indicates that P element can improve the nucleation rate of Si phase during solidification, and further refine the size of Si phase.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec7\" class=\"Section2\"\u003e \u003ch2\u003e3.4 The effect of P on the critical undercooling for growth mode transition\u003c/h2\u003e \u003cp\u003eSince Li et al. [\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e] first applied electromagnetic levitation technology to study the growth morphology and growth mode of semiconductor Si, researchers have investigated a large number of experiments on Si, Ge and their alloys, and it is generally believed that the growth mode of Si will change twice during solidification. In this paper, it is found that the growth mode of Si phase for undercooled Al-60%Si alloy changes twice after adding P element. The first transition is from the lateral growth mode to the mixed growth mode of lateral growth and continuous growth, and the second transition is from mixed growth mode to continuous growth mode.\u003c/p\u003e \u003cp\u003eJian et al. [\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e] constructed a model using parameters such as melting point, thermodynamic equilibrium fraction and entropy of fusion, and theoretical predicted the critical undercooling for growth mode transformation. The critical undercoolings predicted theoretical for undercooled Al-60%Si alloys with various P content was shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e, and found that the critical undercoolings decrease with the increase of P content. Compared with the theoretical predicted results and experimental results which are confirmed by HSV and SEM images, the difference is lower than 5% which indicated that the experimental results match well with the theoretical results.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e"},{"header":"4 Conclusion","content":"\u003cp\u003eAl-60%Si-0.5%P and Al-60%Si-1.0%P alloys were highly undercooled by EML. The growth morphology of Si phase during solidification process was observed and recorded by HSV. The surface morphology of as-solidified alloys was analyzed by SEM. The results show that:\u003c/p\u003e \u003cp\u003e \u003col\u003e \u003cspan\u003e \u003cli\u003e \u003cp\u003eThe Si phase of both Al-60%Si-0.5%P and Al-60%Si-1.0%P alloys present large strip shapes at small undercooling, coarse bulks and regularly arranged dendrites at moderate undercooling, and spheroidal and rod-shaped at large undercooling. There are three growth modes of Si phase is lateral growth, mixed growth and continuous growth.\u003c/p\u003e \u003c/li\u003e \u003c/span\u003e \u003cspan\u003e \u003cli\u003e \u003cp\u003eP can obviously refine the size, morphology, distribution, critical undercoolings of growth mode transition of Si phase. P reacts with Al formed AlP particles, which promotes the nucleation rate of Si phase.\u003c/p\u003e \u003c/li\u003e \u003c/span\u003e \u003cspan\u003e \u003cli\u003e \u003cp\u003eThe critical undercoolings of growth mode transition of Al-60%Si-0.5%P alloy are 86 and 198 K, respectively, and for Al-60%Si-1.0%P alloys are 50 and 162 K, which match well with the theoretical predicted results.\u003c/p\u003e \u003c/li\u003e \u003c/span\u003e \u003c/ol\u003e \u003c/p\u003e"},{"header":"Declarations","content":"\u003ch2\u003eFunding\u003c/h2\u003e \u003cp\u003eThe work was supported by the Scientific Research Program Funded by Shaanxi Province Education Department (No. 23JK0484).\u003c/p\u003e\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eAuthor 1 (B. D.): Investigation, Formal Analysis, Writing - Original Draft; Author 2 (Z.Y. J.): Conceptualization, Funding Acquisition, Supervision, Review \u0026amp; Editing; Author 3 (J.F. X.): Review \u0026amp; Editing.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eDing C, Hao HL, Lu ZG et al (2023) Fabrication of hypereutectic Al-Si alloy with improved mechanical and thermal properties by hot extrusion. Mater Charact 202:113026\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eZhang XG, Chen JY, Zhan Y et al (2024) Interfacial characteristics of dual-phase Si/TiB\u003csub\u003e2\u003c/sub\u003e and its crack initiation mechanism in hypereutectic Al-Si alloys. J Alloy Compd 981:173748\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003ePeng JF, Wang WL, Yuan SJ et al (2024) Improved mechanical and frictional properties of hypereutectic Al-Si alloy by modifying Si phase with La addition. Mater Today Commun 38:107857\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLi CY, Liu F, Yu FX et al (2023) The growth mechanism and morphology evolution of primary Si during slow cooling solidification of high purity Al-15Si alloy with Cr additions. J Mater Res Technol 23:1204\u0026ndash;1213\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eYan PY, Mao WM, Fan J et al (2020) Microstructural evolution, segregation and fracture behavior of A390 alloy prepared by combined Rheo-HPDC processing and Sr-modifier. J Alloy Compd 835:155297\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLi QL, Xia TD, Lan YF et al (2013) Effect of in situ γ-Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e particles on the microstructure of hypereutectic Al-20%Si alloy. J Alloy Compd 577:232\u0026ndash;236\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eTodaro CJ, Easton MA, Qiu D et al (2019) Effect of ultrasonic melt treatment on intermetallic phase formation in a manganese-modified Al-17Si-2Fe alloy. J Mater Process Tech 271:346\u0026ndash;356\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eUzun O, Kilicaslan MF, Yılmaz F (2014) Formation of novel flower-like silicon phases and evaluation of mechanical properties of hypereutectic melt-spun Al-20Si-5Fe alloys with addition of V. Mat Sci Eng A 607:368\u0026ndash;375\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLi QL, Xia TD, Lan YF et al (2013) Effect of rare earth cerium addition on the microstructure and tensile properties of hypereutectic Al-20%Si alloy. J Alloy Compd 562:25\u0026ndash;32\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLan Q, Cheng CL, Zhang JF et al (2019) The relationship between the thermoelectric power and resultant solidification microstructures of Al-Si melt under electromagnetic field. Mater Chem Phys 231:203\u0026ndash;215\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSterner Rainer R Aluminium Silicon Alloy with a Phosphorus Content of 0.001 to 0.1%: US, 1940922[P], 26 Dec.,1933.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eZhu XZ, Wang SH, Dong XX et al (2022) Morphologically templated nucleation of primary Si on AlP in hypereutectic Al-Si alloys. J Mater Res Technol 100:36\u0026ndash;45\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eZhou XL, Zhu XZ, Gao T et al (2016) Evolution of a novel Si-18Mn-16Ti-11P alloy in Al-Si melt and its influence on microstructure and properties of high-Si Al-Si alloy. Results Phys 6:737\u0026ndash;745\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLi D, Herlach DM (1996) Direct measurements of free crystal growth in deeply undercooled melts of semiconducting materials. Phys Rev Lett 77:1801\u0026ndash;1804\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLi DL, Mao XM, Fu HZ (1994) Electromagnetic levitation melting of solar grade silicon material. J Mater Sci Lett 13:1066\u0026ndash;1068\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eWang RY, Lu WH, Hogan LM (1999) Growth morphology of primary silicon in cast Al-Si alloys and the mechanism of concentric growth. J Cryst Growth 207:43\u0026ndash;54\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eXu JF, Diao L, Yan JH et al (2016) In situ observations of the rapid solidification for undercooled Al30Si70 alloy melt. J Mater Res 31:222\u0026ndash;231\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eAoyama T, Kuribayashi K (2001) Rapid solidification processes of semiconductors from highly undercooled melts. Mat Sci Eng A 304\u0026ndash;306:231\u0026ndash;234\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eDang B, Jian ZY, Xu JF (2022) Effect of cerium-rich mischmetal content on the growth morphology and microstructure evolution of undercooled Al-70 wt%Si alloys. Vacuum 205:111427\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eDang B, Jian ZY, Xu JF (2023) Effect of overheating treatment on morphological evolution of highly undercooled Al-70%Si-0.5%RE alloys. Mater Chem Phys 295:127173\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eNagashio K, Okamoto H, Kuribayashi K et al (2005) Fragmentation of faceted dendrite in solidification of undercooled B-doped Si melts. Metall Mater Trans A 36:3407\u0026ndash;3413\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eAoyama T, Takamura Y, Kuribayashi T (1999) Dendrite growth processes of silicon and germanium from highly undercooled melts. Metall Mater Trans A 30:1333\u0026ndash;1339\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBoukellal AK, Elvalli AKS, Debierre JM (2019) Equilibrium and growth facetted shapes in isothermal solidification of silicon: 3D phase-field simulations. J Cryst Growth 522:37\u0026ndash;44\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSpacil I, Gehringer D, Holec D et al (2024) Elucidating effects of Eu and P on solidification and precipitation of Al-7Si-0.3Mg based alloys refined by Ta and TiB\u003csub\u003e2\u003c/sub\u003e. J Alloy Compd 978:173343\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eXiao T, Lv GQ, Bao Y et al (2020) Electromagnetic separation of coarse Al-Si melts: The migration behavior of iron-rich phase and continuous growth of primary silicon. J Alloy Compd 819:153006\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eZhang Q, Liu XF, Dai HS (2009) Re-formation of AlP compound in Al-Si melt. J Alloy Compd 480:376\u0026ndash;381\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eZhu XZ, Wang SH, Dong XX et al (2022) Morphologically templated nucleation of primary Si on AlP in hypereutectic Al-Si alloys. J Mater Res Technol 100:36\u0026ndash;45\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eZhang YR, Gao T, Zhu XZ et al (2015) Refining and nucleating behaviors of AlP on primary phase in Al-Ge and Al-Ge-Si alloys. Mater Charact 99:195\u0026ndash;199\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLi DL, Mao XM, Fu HZ (1994) Electromagnetic levitation melting of solar grade silcion material. J Mater Sci Let 13:1066\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eJian ZY, Kuribayashi K, Jie WQ (2004) Critical undercoolings for the transition from the lateral to continuous growth in undercooled silicon and germanium. Acta Mater 52:3323\u0026ndash;3333\u003c/span\u003e\u003c/li\u003e\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":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"silicon","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"scon","sideBox":"Learn more about [Silicon](https://www.springer.com/journal/12633)","snPcode":"12633","submissionUrl":"https://submission.nature.com/new-submission/12633/3","title":"Silicon","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"Al-Si alloys, Highly undercooled, Morphology evolution, Critical undercooling","lastPublishedDoi":"10.21203/rs.3.rs-4877813/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-4877813/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eIn order to investigate the effect of P content on the growth morphology and the growth mode of Si phase, the Al-60%Si alloys with 0.5%P and 1.0%P was subjected to deep undercooling by electromagnetic levitator. The morphology evolution and growth mode of Si phase was studied by analyzing the dynamic images recorded by HSV and the SEM images of as-solidified samples. The results reveal that the morphology of Si phase changed from the large strip shape to coarse bulks and regularly arranged dendrites, then to spheroidal and rod-shaped with increasing of undercooling, and the corresponding growth mode changed from lateral growth to mixed growth, then to continuous growth. The P refines the size of the Si phase by increasing the nucleation rate of Si phase. With rising of P content, the critical undercoolings of growth mode transition decrease, and the experimental results well match the theoretical predicted results.\u003c/p\u003e","manuscriptTitle":"Effect of phosphorus content on the microstructure evolution of highly undercooled Al-60%Si alloys","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-10-15 08:41:32","doi":"10.21203/rs.3.rs-4877813/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2024-11-05T03:08:11+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2024-10-24T01:05:09+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"181763157629967784693024336729249735244","date":"2024-10-23T19:55:57+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"133832117539341698623193549545804180395","date":"2024-10-14T18:09:15+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"218977555587046607495230509240208831999","date":"2024-10-07T14:30:14+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2024-09-05T02:12:51+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2024-08-22T08:31:22+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2024-08-22T08:29:29+00:00","index":"","fulltext":""},{"type":"submitted","content":"Silicon","date":"2024-08-08T03:28:32+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"silicon","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"scon","sideBox":"Learn more about [Silicon](https://www.springer.com/journal/12633)","snPcode":"12633","submissionUrl":"https://submission.nature.com/new-submission/12633/3","title":"Silicon","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"a8c2b63b-0198-4092-a956-522f58d8c83f","owner":[],"postedDate":"October 15th, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[],"tags":[],"updatedAt":"2025-01-13T16:02:37+00:00","versionOfRecord":{"articleIdentity":"rs-4877813","link":"https://doi.org/10.1007/s12633-024-03219-x","journal":{"identity":"silicon","isVorOnly":false,"title":"Silicon"},"publishedOn":"2025-01-08 15:57:36","publishedOnDateReadable":"January 8th, 2025"},"versionCreatedAt":"2024-10-15 08:41:32","video":"","vorDoi":"10.1007/s12633-024-03219-x","vorDoiUrl":"https://doi.org/10.1007/s12633-024-03219-x","workflowStages":[]},"version":"v1","identity":"rs-4877813","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-4877813","identity":"rs-4877813","version":["v1"]},"buildId":"qtupq5eGEP_6zYnWcrvyt","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}