铸态AZ61镁合金热压缩变形组织变化

Microstructure in as-cast AZ61 magnesium alloy during hot compression deformation

利用Gleeble-1500对铸态AZ61镁合金在变形温度200-500℃,应变速率0.001-1s^-1的条件下进行压缩变形;利用显微结构分析和硬度测试等研究不同变形条件下AZ61镁合金的组织和性能,引用Z值（Zener-Hollomon系数）研究温度和应变速率对AZ61镁合金组织的影响,建立再结晶晶粒尺寸与Z值之间的关系。结果表明：铸态AZ61镁合金在热变形时表现出动态再结晶特征,随温度上升,再结晶容易发生且峰值应力降低,再结晶晶粒尺寸随温度升高而增大;随应变速率上升,峰值应力增大且峰值应力对应的应变量增大,再结晶晶粒尺寸减小;硬度大小的变化也与动态再结晶密切相关。

Thermal compression tests of as-cast AZ61 magnesium alloy were performed at deformation temperature between 200 - 500℃ and strain rate between 0.001 - 1s^-1 . Microstructure and mechanical properties of the alloy were studied by means of metallography analysis and hardness test under different deformation conditions. The effects of temperature and strain rate on the mierostructure evolution of as-cast AZ61 magnesium alloy were analyzed by introducing temperature-compensated strain rate （Zener-Hollomon parameter）. The function relation between dynamic recrystallization （DRX） grain size and the value of Z was built. The results show that DRX of AZ61 alloy occurs under compression deformation. DRX becomes easier, values of stress peak decrease and the DRX grain size grows up with the deformation temperature increasing.The values of stress peak and the critical strain increases and the DRX grain size gets smaller with the strain rate increasing. The change of values of hardness closely link to the DRX.