退火参数对ZE42镁合金热挤压板显微组织结构的影响

采用光学显微镜和TEM观察等方法,分析了ZE42镁合金热挤压板材在不同退火温度和时间条件下的显微组织结构。结果表明:该合金板材经过退火热处理后均发生明显的再结晶组织转变,晶粒尺寸在10～60μm之间,合金基体中存在大量含有稀土元素的第二相颗粒,这些第二相在热变形过程中破碎成细小的颗粒,促进了再结晶晶粒的形核。当退火温度一定时,随着保温时间的延长,该合金板材的平均晶粒尺寸首先增加,随后少量减小,最后又随退火时间的增加而增加;当保温时间一定时,随着退火温度的增加,晶粒平均尺寸持续增加,并且温度越高,增长速率越大。同时,通过晶粒长大动力学分析和计算建立了该合金再结晶晶粒长大的动力学模型,通过计算可知:该合金的再结晶晶界迁移激活能为15.32 kJ·mol-1。

Effect of Annealing Parameters on Microstructures of Thermally Extruded ZE42 Magnesium Alloy Plate

The microstructure of extruded ZE42 alloy plate annealed at different temperature and holding time was investigated by using optical microscope and TEM.The results showed that visible recrystallization transformation occurred and recrystallized grains(10~60 μm) were obtained in the magnesium alloy plates after different annealing processing,and lots of second phase containing rare earth elements in alloy matrix were destroyed into small particles during thermally deformation,which stimulated the nucleation of dynamic recrystallized(DRX) grains.When the annealing temperature was constant,the average size of grains firstly grew,followed by a small decrease,and finally increased with increasing of annealing time.However,when the annealing time was constant,the average size of grains grew with increasing of annealing temperature,and the increase rate of grains increased with increasing annealing temperature.Meanwhile,the growth model of recrystallized grains was established by the dynamic analysis and calculation,and the activation energy of grain boundaries migration was calculated to be 15.32 kJ · mol-1.