大塑性变形的AM60镁合金半固态等温处理研究

Research on semi-solid isothermal treatment of AM60 magnesium alloy processed by severe plastic deformation

为了制备晶粒细小且球化程度高的的AM60镁合金半固态坯料,对铸态和等径道角挤压态的AM60镁合金半固态等温处理过程进行了研究.借助金相显微镜对AM60镁合金铸坯和等径道角挤压后的铸坯在半固态等温处理中的微观组织演变进行了观察.研究结果表明:对于AM60镁合金,直接等温处理获得的半固坯晶粒很粗大,其平均晶粒尺寸都在100μm以上,晶粒球化效果不理想,很难获得合格的半固态坯;新SIMA法是一种非常理想制备AM60镁合金半固态坯的方法,利用该方法制备的AM60半固态坯的微观组织晶粒十分细小,平均晶粒尺寸在8～22μm,晶粒球化程度高;随着保温时间的延长,新SIMA法制备的AM60半固态坯的微观组织出现长大现象;随着等温处理温度的升高,固相晶粒的平均尺寸先增加后减小,晶粒球化程度越来越高.

In order to prepare AM60 magnesium alloy semi-solid billet with fine spheroid grains,isothermal treatment processs of as-cast billets and billets processed by equal channel angular extrusion（ECAE） was investigated.By means of metalloscope,microstructure evolution of as-cast billets and billets processed by ECAE was observed.The results show that coarse grains with the grain size more than 100 μm exist in semisolid billet prepared by isothermal treatment of as-cast AM60 magnesium alloy.Furthermore,spheroidization is not desirable,which indicates it is not good method.Fine grains with grains size ranging from 8 μm to 22 μm and high spheroidization can be obtained in semi-solid billets prepared by new SIMA.With increasing holding time,growing trend occurs in semi-solid billets prepared by new SIMA.With elevating temperature,grains size of solid phase of semi-solid billet first increases and then decreases and spheroidization becomes better and better.