Effect of trace Bi addition on the microstructure and mechanical properties of hypoeutectic Al-Mg-Si-Mn alloy

• Published in: Materials today communications 2024-12, Vol.41, p.110954, Article 110954
• Main Authors: Jiang, Feng, Wang, Hong-ding, Xiang, Qing-chun, Ren, Ying-lei, Meng, Fan-xu, Qu, Ying-dong, Qiu, Ke-qiang
• Format: Article
• Language: English
• Subjects: AlMg5Si2Mn alloy; Bi modification; Eutectic Mg2Si phase; Mechanical properties
• ISSN: 2352-4928; 2352-4928
• DOI: 10.1016/j.mtcomm.2024.110954

The effects of Bi on the eutectic structure and mechanical properties of AlMg5Si2Mn alloy were investigated. The results show that when trace Bi is added to the alloy, the eutectic Mg2Si phase in the alloy is successfully refined from long plate-like to fine fiber rod-like and coral-like structure. It is mainly attributed to the precipitation of Bi atomic clusters on the front of the solid-liquid interface and form a component supercooling, in which part of Bi atoms react with Mg atoms to form nanosized Mg3Bi2 particles, which effectively inhibits the rapid growth of eutectic Mg2Si and promotes the branching and refining of eutectic Mg2Si. The strength and ductility of AlMg5Si2Mn alloy containing Bi are significantly improved simultaneously. Compared to the unmodified alloy, the largest tensile strength, yield strength and elongation to failure of the 0.3 wt% Bi-modified alloy are increased to 28.04 %, 12.3 % and 129.1 %, respectively. The fracture mode of the alloy changes from brittle fracture to ductile fracture. [Display omitted] •The eutectic Mg2Si in hypoeutectic AlMg5Si2Mn alloys were modified by Bi addition.•The mechanical properties of hypoeutectic AlMg5Si2Mn alloys with Bi addition were significantly improved.•The Bi-rich clusters and Mg3Bi2 nanoparticles restrained the rapid growth of eutectic Mg2Si in the alloy.