ZK60镁合金均匀化过程中的组织演变

Microstructure Evolution of ZK60 Magnesium Alloy during Homogenization

采用光学显微镜、扫描电镜、能谱分析和X射线衍射研究了ZK60镁合金铸态的显微组织以及均匀化过程中的组织演变与成分分布。结果表明:ZK60铸态合金中枝晶偏析严重,在晶界和枝晶边界处存在大量的非平衡共晶相,其主要成分为α-Mg和Mg7Zn3;经过均匀化处理后,合金中的非平衡相随温度的升高和时间的延长逐渐溶解,但温度高于420℃后发生过烧,最佳均匀化处理制度为400℃/12h,该制度与均匀化动力学方程所得结果基本一致。

The microstructure evolution and composition distribution of as-cast and homogenized ZK60 magnesium alloy were investigated by optical microscope,scanning electron microscope,energy dispersive X-ray diffraction and X-ray diffraction.The results show that serious dendrite segregation is existed in the ZK60 alloy ingot,a number of non-equilibrium eutectic phases which mainly contain α-Mg and Mg3Zn7 are segregated at the grain boundaries and between dendrites boundaries.The non-equilibrium eutectic phases are dissolved gradually with the increasing temperature and holding time after the homogenization process,and the dendrite segregation is eliminated.However,the alloy is over-burnt when the temperature is over 420℃.The optimal homogenization regime is suggested to be 400℃/12h,which is basically consistent with the result obtained by homogenizing kinetics equation.