等温热处理对挤压态镁锂合金组织、硬度及延伸率的影响

Effects of isothermal heat treatment on the microstructure hardness and extension rate of extruded Mg-Li alloy

采用氩气氛下感应熔炼和正向挤压变形制备了Mg-7.5Li-3.5Al-1Zn-1Ce-0.5Sn镁锂合金板材,然后在真空热处理炉中对挤压态合金进行等温退火,并采用金相观察和布氏硬度测试研究了等温热处理对合金板材显微组织和布氏硬度的影响.通过金相显微镜观察表明,等温处理温度对合金显微组织的影响较大,在较低温度下,只发生两相的形态和体积分数的变化,合金几乎不发生或需要较长时间才发生静态再结晶.在较高温度下,合金快速发生再结晶,合金晶粒细化,但随着保温时间的延长,晶粒有所长大.不同的组织形态对应的硬度不同,α相呈球化时的硬度值最高.

The Mg-7.5Li-3.5AI-IZn-ICe-0.5Sn alloy sheet was manufactured by induction melting ＆ casting under the atmosphere of argon and hot extrusion, isothermal annealing was applied to the extruded alloy inside a vacuum furnace, and metallographic observation and BrineU hardness test were used to research the influence of isothermal heat treatment on the microstructure and Brinell hardness of the alloy sheet. It is indicated by the metallographic microscope observation that the isothermal treatment temperature greatly affected the microstructure of the alloy. Under a low temperature, only the changes of two phases of shape and volume fraction occurred, while the static recrystallization almost didn＇t happen or only occurred after a long time. Under a high temperature, the recrystallization happened in the alloy rapidly, and the grain of the alloy became thin. With the increase of holding time, the grain grew up. Different microstructure corresponded to different hardness. The hardness was the highest when the a phase was spheroidized.