中文摘要：

采用硬度检测、拉伸试验、TEM、SEM观察等方法对于两种经过冷热循环处理后的铸态镁合金AZ91和ZK60在力学性能及微观组织的变化进行了研究。研究结果表明：冷热循环处理比单独热处理或深冷处理能更有效提高合金力学性能,对于AZ91镁合金深冷处理24 h＋T6效果最明显,对ZK60合金,深冷处理16 h＋T6的循环处理则是最佳工艺。冷热循环处理后改变了AZ91合金中β-Mg17Al12相的数量和形貌,而在ZK60合金组织中则发现了细小的杆状相和碟状相析出。

英文摘要：

Effects of thermal-cold cycling treatment on microstructure and mechanical properties of AZ91 and ZK60 as-cast magnesium alloys were investigated by hardness test,tensile test and microstructure analysis.The results show that the mechanical properties of the samples treated by thermal-cold cycling treatment are higher than those of just T6 treated or deep cryogenic treated samples.The optimum heat treatment process are deep cryogentic treatment（24 h）＋T6 for AZ91 alloy and deep cryogentic treatment（16 h）＋T6 for ZK60 alloy,respectively.The improvement of mechanical properties of AZ91 alloy is contributed to that the number and shape of β-Mg17Al12 changed,while in ZK60 alloy,the increased density of rod-like and disc-shaped precipitates are the main reasons.