Microstructural and Morphological Evolution of Novel In Situ Al-15%Mg₂Si-4.5%Si Composite with Strontium Addition

Abstract:

This study investigates the effect of Sr (0.1, 0.15, and 0.2 wt.%) modification on the microstructure and morphological evolution of the in-situ Al-15%Mg₂Si-4.5%Si composite. The composites are developed via Low superheat casting (LSC) technique, at the onset of gravity, and subsequently characterized through optical microscope, X-ray Diffraction (XRD), Scanning Electron Microscope (SEM), Electron Probe Microprobe Analysis (EPMA), and XRD texture analysis. It is found that, with the increase of Sr content in the Al-15%Mg₂Si-4.5%Si composite, the morphology of primary Mg₂Si particles changes from irregular dendritic and hopper structure to nearly perfect cubic morphology. The addition of 0.2 wt.% Sr reduces the average primary magnesium silicide (Mg₂Si) particle size from ~56 µm to 36 µm and the Al grain size from ~63 µm to ~44 µm, indicating significant refinement. The XRD texture analysis through Orientation Distribution Function (ODF) reveals that the cubic texture and rotated cubic texture are the predominant orientations for Al and Mg₂Si phases, respectively. However, the composite modified with 0.2 wt.% Sr exhibits a weak texture and more random grain distribution, highlighting the role of Sr in reducing grain size and promoting uniformity. These findings underscore the potential of Sr addition to enhance the microstructural and mechanical properties of Al-15Mg₂Si-4.5Si composites for advanced applications.

• Periodical: Materials Science Forum (Volume 1176)
• Pages: 7-13
• DOI: https://doi.org/10.4028/p-E7yFb9
• Online since: January 2026
• Authors: Mohammed Kedir, Prosenjit Das*
• Keywords: In Situ Composite, Magnesium Silicide, Microstructure, Morphology

References

[1] J. Zhang, Z. Fan, Y.Q. Wang, B.L. Zhou, Equilibrium pseudobinary Al–Mg2Si phase diagram, Mater. Sci. Technol. 17 (2001) 494–496.

[2] Q.D. Qin, Y.G. Zhao, C. Liu, P.J. Cong, W. Zhou, Strontium modification and formation of cubic Mg2Si crystals in Mg2Si/Al composite, J. Alloys Compd. 454 (2008) 142–146.

DOI: 10.1016/j.jallcom.2006.12.074

[3] C. Li, Y. Wu, H. Li, X. Liu, Microstructural formation in hypereutectic Al–Mg2Si with extra Si, J. Alloys Compd. 477 (2009) 212–216.

DOI: 10.1016/j.jallcom.2008.10.061

[4] S.C. Tjong, Z.Y. Ma, Microstructural and mechanical characteristics of in situ metal matrix composites, Mater. Sci. Eng. R Rep., 29 (2000) 49-113.

DOI: 10.1016/s0927-796x(00)00024-3

[5] N. Soltani, A. Bahrami, M.I. Pech-Canul, The Effect of Ti on Mechanical Properties of Extruded In-Situ Al-15 pct Mg2Si Composite, Metall. Mater. Trans. A 44 (2013) 4366-4373.

DOI: 10.1007/s11661-013-1747-2

[6] M. Emamy, R. Khorshidi, A.H. Raouf, The influence of pure Na on the microstructure and tensile properties of Al–Mg2Si metal matrix composite. Mater. Sci. Eng. A 528 (2011) 4337–4342.

DOI: 10.1016/j.msea.2011.02.010

[7] D.K. Yadav, M. Mahali, S.K. Gupta, I. Chakrabarty, Microstructural characterization and mechanical behavior of Al-4 wt% Mg2Si in-situ metal matrix composite synthesis via cooling slope casting technique, Mater. Today Proc. 62 (2022) 442–447.

DOI: 10.1016/j.matpr.2022.03.564

[8] N. Nasiri, M. Emamy, A. Malekan, M.H. Norouzi, Microstructure, and tensile properties of cast Al-15%Mg2Si composite, Effects of phosphorous addition and heat treatment, Mater. Sci. Eng. A 556 (2012) 446–453.

DOI: 10.1016/j.msea.2012.07.011

[9] Y.G. Zhao, Q.D. Qin, W. Zhou, Y.H. Liang, Microstructure of Ce-modified in situ Mg2Si/Al-Si-Cu Composite, J. Alloys Compd. 389 (2005) L1-L4.

DOI: 10.1016/j.jallcom.2004.08.003

[10] J. Zhang, Z. Fan, Y.Q. Wang, B.L. Zhou, Microstructural development of Al-15wt%Mg2Si in situ composite with mischmetal addition, Mater. Sci. Eng. A 281 (2000) 104-112.

DOI: 10.1016/s0921-5093(99)00732-7

[11] C.J. Song, Z.M. Xu, J.G. Li, Fabrication of in situ Al/Mg2Si functionally graded materials by electromagnetic separation method, Compos. Part A Appl. Sci. Manuf. 38 (2007) 427–433.

DOI: 10.1016/j.compositesa.2006.03.002

[12] H.Y. Wang, W. Wang, M. Zha, N. Zheng, Z.H. Gu, D. Li, Q.C. Jiang, Influence of the amount of KBF4 on the morphology of Mg2Si in Mg–5Si alloys, Mater. Chem. Phys. 108 (2008) 353–358.

DOI: 10.1016/j.matchemphys.2007.10.006

[13] R.E.N. Bo, Z.X. Liu, R.F. Zhao, T.Q. Zhang, M.X. Wang, Y.G. Weng, Effect of Sb on microstructure and mechanical properties of Mg2Si/Al-Si composites, Trans. Nonferrous Met. Soc. China 20 (2010) 1367-1373.

DOI: 10.1016/s1003-6326(09)60306-x

[14] P. Das, Optimisation of melt pouring temperature and low superheat casting of Al-15Mg2Si-4.5Si composite. Int. J. Cast Met. Res. 36 (2023) 76-89.

DOI: 10.1080/13640461.2023.2211895

[15] M. Kedir, P. Das, Development of Low superheat cast In-situ Al-xMg2Si-ySi composite and investigation of its microstructure and mechanical properties. Mater. Today Commun. 43 (2025) 111807.

DOI: 10.1016/j.mtcomm.2025.111807

[16] J. Zhang, Y.Q. Wang, B. Yang, B.L. Zhou, Effect of Si Content on the Microstructure and Tensile Strength of an In Situ Al/ Mg2Si Composite, J. Mater. Res. 14 (1999) 68–74.

DOI: 10.1557/jmr.1999.0012