Ca和Sr元素对高应变速率轧制Mg-5Zn合金动态再结晶和力学性能的影响

摘要

利用光学显微镜、扫描电子显微镜、热压缩试验以及拉伸实验研究Ca、Sr元素单一添加以及复合添加对铸态和轧制态Mg?5Zn合金显微组织和力学性能的影响.Ca元素在铸态组织中细化晶粒尺寸的作用比Sr元素明显.高应变速率轧制过程中产生大量的变形孪晶,因此提供大量的动态再结晶形核点.高应变速率轧制过程中,Ca、Sr元素会促进动态析出相的析出,而动态析出相的析出会消耗部分储存能,因此提高了动态再结晶的临界应变值,延迟了动态再结晶的产生.轧制态Mg?5Zn?0.4Ca?0.2Sr合金具有良好的综合力学性能,其极限抗拉强度、屈服强度、断后伸长率分别是317 MPa、235 MPa和24％.%Effects of the sole and the combined addition of Ca and Sr on microstructure and mechanical properties of as-cast and as-rolled Mg?5Zn alloys were carefully investigated by OM, SEM, hot-compression testing and tensile testing. Ca is more effective than Sr in the microstructural refinement of as-cast alloys. High-strain-rate rolling (HSRR) produces more deformed twins and thus provides more nucleation sites for dynamic recrystallization (DRX). The addition of Ca and Sr can promote dynamic precipitation during HSRR, the precipitation process would consume the storage energy and thus increases the critical strain value of DRX, resulting in the retarded DRX effect by the addition of Ca and/or Sr. The as-rolled Mg?5Zn?0.4Ca?0.2Sr alloy exhibits a good combination of strength and ductility, with the ultimate tensile strength of 317 MPa, the yield strength of 235 MPa and the elongation to rupture of 24％.