AZ31镁合金热变形时的显微组织与断口分析

The Microstructure and Fracture Analysis of AZ31 Magnesium Alloy during Thermal Deformation

在不同温度下对AZ31镁合金薄板进行了单向拉伸实验,采用金相显微镜观察了其拉伸变形后的显微组织,并利用扫描电镜对不同温度下的拉伸断口进行了观察。结果发现,在变形过程中发生了动态再结晶。随变形温度的升高,显微组织中再结晶晶粒增多,当温度为250℃时显微组织以动态再结晶晶粒为主,且晶粒细小均匀,而当温度高于250℃后,晶粒长大。断口分析表明:250℃左右变形时,合金进入多系滑移阶段,滑移变得容易,断口呈韧性断裂。因此,认为250℃左右是AZ31镁合金薄板进行塑性成形的最佳温度。

Uni-axial tensile test has been condueted on AZ31 magnesium alloy sheet at different temperatures. The mierostructures after tension have been observed by use of microscope, and the fracture surfaces of tensile samples have been investigated by SEM. It is found that dynamic re-crystallization （DRX） occurs dur/ng the deformation. DRX grains increase as the deformation temperature is higher. The microstructure after tensile at 250℃ mostly consists of fine and uniform DRX grains. The DRX grains grow larger when the temperature is higher than 250℃. Fractographic analysis show that when tile tensile test on AZ31 sheet is conducted at around 250℃ , the fracture surface shows ductile character beeause the internal slip systems are all started-up, and the slip gets easy. It is concluded that the best plastic forming temperature for AZ31 sheet is around 250℃.