采用自制装置对AZ81镁合金进行压入蠕变实验,通过建立稳态压入蠕变本构模型分析合金的蠕变机制,利用扫描电镜（SEM）和X射线衍射（XRD）等方法研究合金蠕变前后的组织和成分。结果表明：压铸AZ81合金在稳态蠕变阶段的应力指数n为2.08,蠕变激活能QC为87.26 kJ/mol;蠕变诱导β相首先由非连续方式析出,到达一定程度后连续析出;沿晶界析出的β相导致合金抗蠕变性能降低;蠕变温度越高,基体和析出相的晶粒尺寸越大;压铸AZ81合金的压入蠕变机制为晶界扩散主导的位错交滑移运动。
Impression creep property of AZ81 magnesium alloy was investigated by a special apparatus.The impression mechanism of the alloy was analyzed by constructing constitutive equations of the impression steady creep.The microstructure and composition of precipitated phases of the alloy before and after creep were analyzed by scanning electron microscopy（SEM）and X-ray diffraction（XRD）.The results show that the stress exponent n of die-cast AZ81 alloy is 2.08 and creep activation energy QC is 87.26 kJ/mol.Firstly Mg17Al12（β） phase is precipitated discontinuously,and then continuous precipitation of Mg17Al12 phase gadually occurs in the process of the impression creep.It can be seen from the SEM images that the creep resistance of the alloy decreases because of the precipitation of Mg17Al12 phase at grain boundaries.The higher the creep temperature is,the larger the size of matrix grains and precipitated phase is.The impression creep mechanism of die-cast AZ81 alloy is dislocation slipping by grain boundary diffusion.
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