挤压态Mg-0.5Bi-0.5Sn-0.5Ag合金的热变形行为、组织和织构演变

Hot deformation behavior,microstructure and texture evolution of extruded Mg-0.5Bi-0.5Sn-0.5Ag alloy

本文成功制备了一种新型挤压态低合金化Mg-0.5Bi-0.5Sn-0.5Ag合金(BTQ000合金)。在变形温度为400℃、应变速率为10 s^(-1)的条件下,对BTQ000合金进行热压缩实验,研究了该合金在不同应变阶段的变形机制组织和织构演变。结果表明:BTQ000合金的流变应力曲线可分为加工硬化、动态回复、稳态流变和额外应变硬化四个阶段。合金发生了明显的回复和动态再结晶,随着应变的增大,平均晶粒粒径先增大后减小,孪晶的面积分数逐渐减小,亚晶的面积分数先增后减。当应变为0.1时,亚晶的最大面积分数为76.2%,亚晶对织构类型和强度起着主导作用,而织构强度则表现出先减后增的趋势。当应变为0.4时,大量具有弥散取向的动态再结晶晶粒减少了织构的峰值强度。由此可见,亚晶和动态再结晶是影响合金织构类型和强度的主导因素。

A novel Mg-0.5Bi-0.5Sn-0.5Ag alloy(BTQ000 alloy)was developed and fabricated through extrusion.Hot compression experiments of BTQ000 alloy were carried out at a deformation temperature of 400℃and a strain rate of 10 s^(-1).The deformation mechanism,microstructure and texture evolution of the alloy at different strain stages were studied.The results show that the flow stress profile of BTQ000 alloy can be divided into four stages:work hardening,dynamic recovery,steady state and extra strain hardening.The alloy has obvious recovery and dynamic recrystallization.With the increase of strain,the average grain size first increases and then decreases,while the area fraction of twin crystals gradually declines.The area fraction of sub-grains initially increases before declining.When the strain is 0.1,the area fraction of sub-grains reaches the maximum of 76.2%.The sub-grains play a dominant role in determining the type of texture and strength,while the texture strength shows a trend of decreasing initially before increasing.When the strain is 0.4,the large number of dynamic recrystallized grains with dispersed orientation reduce the peak strength of texture,thus showing that sub-grains and dynamic recrystallisation distribution grains are the dominant factors that influence the type of texture and strength of the alloy.