Microstructure and Mechanical Properties of Mg{sub 2}Si/AZ91 Composites In Situ Synthesized by Using Silica Fume as the Si Source
- Shanghai Jiao Tong University, State Key Laboratory of Metal Matrix Composites, School of Materials Science and Engineering (China)
- No. 52 Institute of China Ordnance Industries Group (China)
Microstructure and mechanical properties of in situ Mg{sub 2}Si/AZ91 composites fabricated using silica fume as the Si source were investigated. The composites contained α-Mg, network Mg{sub 17}Al{sub 12}, lamellar Mg{sub 17}Al{sub 12}, coarse polygonal Mg{sub 2}Si and needle-type Mg{sub 2}Si. Mischmetal modification eliminated the coarse polygonal Mg{sub 2}Si and resulted in a decreased amount of lamellar Mg{sub 17}Al{sub 12} and refined matrix grain size. Solution and aging treatment made the network Mg{sub 17}Al{sub 12} transform into lamellar Mg{sub 17}Al{sub 12}. As the volume fraction of Mg{sub 2}Si increased, the matrix grain size decreased, the amount of Mg{sub 17}Al{sub 12} increased, and more Mg{sub 17}Al{sub 12} precipitated in grain interiors as a result of the increased Al/Mg ratio caused by increasing the amount of Mg{sub 2}Si. The tensile strength and elastic modulus were much higher for the modified composites than for the unmodified one and increased by both increasing the volume fraction of Mg{sub 2}Si and performing aging treatment. The composites failed in a quasi-cleavage fracture mode, and coarse polygonal Mg{sub 2}Si phases were responsible for the lowest ductility of the unmodified composite. The highest UTS of 291.55 MPa obtained is much higher than those reported so far by using fly ash as the Si source, indicating that silica fume is more suitable as the Si source to synthesize Mg{sub 2}Si/AZ91 composites.
- OSTI ID:
- 22863246
- Journal Information:
- Journal of Materials Engineering and Performance, Vol. 27, Issue 10; Conference: EUROMAT 2017: European Congress and Exhibition on Advanced Materials and Processes, Thessaloniki (Greece), 17-22 Sep 2017, AeroMat 2017: Advanced Aerospace Materials and Processes Conference and Exposition, Thessaloniki (Greece), 17-22 Sep 2017; Other Information: Copyright (c) 2018 ASM International; http://www.springer-ny.com; Country of input: International Atomic Energy Agency (IAEA); ISSN 1059-9495
- Country of Publication:
- United States
- Language:
- English
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