可时效强化Mg-Sn基合金的研究进展

Research Progress in Age-Hardenable Mg-Sn Based Alloys

Mg-Sn基合金是可时效强化镁合金,主要析出相是Mg2Sn。Mg-Sn二元相图中富Mg端的共晶温度显著高于Mg-Al和Mg-Zn二元相图中富Mg端的共晶温度,与Mg-RE的相近,有望发展成为不含稀土的低成本耐热镁合金。本文系统总结了可时效强化Mg-Sn基合金的研究进展,澄清了该类合金组织研究中的基本问题,梳理了合金化的发展脉络,全面且深入地分析了Mg/Mg2Sn固态相变系统的特征,并对Mg-Sn基合金未来的研究进行了展望。

Mg-Sn based alloy system is a typical age-hardenable Mg alloy system with Mg2 Sn as the major precipitation phase. Eutectic temperature at Mg-rich end of Mg-Sn phase diagram is much higher than those of Mg-Al and Mg-Zn phase diagrams, which is comparable to that of Mg-RE phase diagram.So Mg-Sn based alloys are hopeful candidates of rare-earth free heat resistant Mg alloys with low cost.This paper systematically reviews research progress in age-hardenable Mg-Sn based alloys. The main second phase β-Mg2 Sn has a fcc structure with different lattice parameters reported, one of which the most frequently adopted is aβ≈0.676 nm, agreeing well with calculations of interfacial orientations. Twelve orientation relationships(ORs) between Mg2 Sn precipitates and Mg matrix have been identified. Those with similar morphologies, i.e., the same long axis direction or the same habit plane, are possibly related to different ORs. Addition of Zn benefits the appearance of β-Mg2 Sn precipitates inclined to the Mg basal plane, which are more effective to hinder dislocation movement on the basal plane and result in a greater strengthening effect. Effects of various alloying elements on age-hardening response and mechanical properties of Mg-Sn binary alloys have been summarized. Elements such as Zn, Al, Ag and Na can enhance age-hardening responses. Due to formation of highly thermal stable compounds with Sn, RE, Ca,Sr and Li exhibit negative effects. Consequently, alloy design of Mg-Sn based alloys faces more difficulties, requiring an in-depth investigation of phase transformation processes. Finally, future research directions have been specified.