通过对热轧的ZK61镁合金板材试样分别进行不同温度和不同保温时间的退火实验,利用金相显微镜(OM)观察显微组织,对晶粒尺寸进行分析和处理,并建立数学模型,系统研究了轧制ZK61镁合金的晶粒长大行为.研究结果表明,晶粒尺寸随着退火温度的升高与退火时间的延长而粗化,退火温度对晶粒长大的影响比退火时间的影响明显.对于ZK61镁合金在250～450℃温度区间的晶粒长大过程,其晶粒尺寸与加热时间的关系可用Beck方程Dn-Don=kt描述,其中k=koexp[-Qg/(RT)].计算可得晶粒长大指数n为3.5,长大激活能Qg为45 kJ/mol.
The annealing experiment of the hot-rolled ZK61 magnesium alloy plates was carried out under different annealing temperature and holding time.The microstructure was observed by optical microscope (OM),and the mathematical model for the relationship among the grain size,annealing temperature and holding time was established to investigate the grain growth behavior of hot-rolled ZK61 magnesium alloy.The results indicate that the increasing annealing temperature and the extending holding time can lead to the coarsened grain.In addition,annealing temperature apparently has a greater effect on the grain growth than holding time.The relationship between the grain size and holding time of ZK61 magnesium alloy in the temperature range of 250-450 ℃ can be well interpreted by the kinetic equation,Dn-D0 n =k t,where k =k0 exp[-Qg/(RT)].And the calculated grain growth exponent (n) and the activation energy (Qg) are about 3.5 and 45 kJ/mol,respectively.
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