高强Mg-Gd-Y-Zn-Zr合金的微观组织和力学性能

摘要

High-strength Mg-7Gd-4Y-1.6Zn-0.5Zr alloy was prepared by conventional metal mold casting, subsequently hot extrusion and T5 heat treatment were conducted. The microstructures and mechanical properties of this Mg alloy under different states were studied by using OP, XRD, SEM and TEM. The results show that the as-cast microstructures of Mg-7Gd-4Y-1.6Zn-0.5Zr alloy consists of a-Mg matrix and lamellar second-phase Mg12Zn(Gd, Y) phase which distributes around a-Mg matrix. After hot extrusion, the grain size of this alloy can be refined dramatically. Tiny little particle Mg3Zn3(Gd, Y)2 phase is precipitated out of the Mg12Zn(Gd, Y) phase during the process of T5 heat treatment. The tensile strength, yield strength and elongation of alloys under T5 condition reach 446 Mpa, 399 Mpa and 6.1%, respectively. The main strengthening methods are considered as fine grain strengthening and second-phase strengthening.%通过金属模铸、热挤压和时效处理(T5)工艺过程制备出高强Mg-7Gd-4Y-1.6Zn-0.5Zr合金,并利用光学显微镜、XRD、SEM及TEM分析研究Mg合金不同状态下的显微组织和力学性能.结果表明:Mg-7Gd-4Y-1.6Zn-0.5Zr合金的铸态组织主要由a-Mg基体和沿晶界分布的片层状第二相Mg12Zn(Gd,Y)组成,经过热挤压变形后,合金晶粒显著细化,时效处理过程中Mg12Zn(Gd,Y)相上析出少量细小的颗粒状Mg3Zn3(Gd,Y)2相.时效态合金的抗拉强度、屈服强度和伸长率分别达到446 MPa、399 MPa和6.1％,其强化方式主要为细晶强化和第二相强化.