固溶处理对Mg-xZn-2Gd合金组织及性能的影响

Effects of Solution Treatment on Microstructure and Mechanical Properties of Mg-x Zn-2Gd Alloy

用铸造法制备不同Zn含量的Mg-x Zn-2Gd合金,利用光学显微镜和扫描电镜对Mg-x Zn-2Gd合金的显微组织进行分析,采用室温拉伸实验对合金的力学性能进行测试。结果表明,Mg-Zn-Gd相沿晶界析出。随Zn含量的增加,铸态Mg-x Zn-2Gd合金的平均晶粒尺寸减小,第二相含量增多,屈服强度和抗拉强度升高。当Zn含量达到4wt%时,合金的力学性能达到峰值。经固溶处理后,第二相溶解,并随保温时间的延长,合金的显微硬度逐渐降低,在24 h时达到极小值。铸态Mg-4Zn-2Gd合金在430℃下进行固溶处理24 h后,屈服强度和抗拉强度降低,伸长率上升,为后续热挤压加工提供了良好的组织状态和力学性能。

The Mg-x Zn-2Gd alloys with different Zn content were obtained by casting. The microstructure of Mg-x Zn-2Gd alloy was studied by OM and SEM, and tensile properties were tested at room temperature. The results indicate that the Mg-Zn-Gd phase precipitates along grain boundaries. With the increase of Zn content, the average grain size of as-cast Mg-x Zn-2Gd alloy decreases and the amount of the secondary phase increases, which results in the improvement of YS and UTS. The best mechanical properties are obtained in Mg-4Zn-2Gd alloy, when Zn content reaches by 4wt%. The secondary phase dissolves into the alloy after solution treatment. With the increase of solution time, the micro-hardness decreases and the minim value is obtained at 24 h. When alloy as-cast is treated at 430℃ and 24 h, the YS and UTS decrease, while the ductility increases. It provides good microstructure and mechanical properties for subsequent hot extrusion.