通过Gleeble高温热模拟实验,采用加工图理论分析了AZ31镁合金在中温变形过程中的流变失稳特征.结果表明:AZ31镁合金在250℃进行塑性变形时,应变速率不同将出现不同的变形组织,其规律与一般金属的存在显著差别;在低应变速率(小于0.15 s-1)条件下,显微组织出现大晶粒被细小晶粒包围的"项链"组织特征;当变形量足够大时,塑性变形协调机制不能满足,出现流变失稳,试样开裂;随着应变速率的提高,由于孪生变形机制的激活,大晶粒产生孪生变形,使晶界处的应力集中得到缓解,塑性流变过程逐渐稳定.
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