轧前深冷处理对AZ31镁合金显微组织和力学性能的影响

本文通过对铸态AZ31镁合金经不同条件的深冷处理继而热轧,分析其强度、韧性、延展性效应及其规律。深冷实验条件分别为-60℃/12h、-120℃/12h、-180℃/12h、-60℃/2h和-180℃/2h。结果表明：AZ31经适宜的深冷处理,晶粒得到细化,强度、韧性及延展性得到有效提高；与未经深冷处理试样相比,深冷处理时间为2h的两种试样中都出现大量孪晶；经-60℃/12h深冷处理后再进行轧制试样的显微组织最为细小均匀,屈服强度提高了25.8%,而延伸率则更是提高了4倍,由3.06%提高到了12.31%；深冷处理后的AZ31镁合金断口呈现出脆性断裂和塑性断裂集合的复合性断裂特征。

Effect of cryogenic treatment prior rolling on microstructure and mechanical properties of AZ31 magnesium alloy

The effects of cryogenic treatment prior hot rolling on the strength toughness and ductility of as-cast AZ31 magnesium alloy plate was investigated in this study. The cryogenic treatment conditions were ?60 °C/12 h, ?120 °C/12 h, ?180 °C/12 h, ?60 °C/2 h, and ?180 °C/2 h. Experimental results indicated that appropriate cryogenic treatment conditions can significantly refine the grain size and the strength, toughness and ductility were also improved. A large number of twins appeared in both kinds of samples cryogenically treated for 2 h. The grain size of the sample, which experienced cryogenic treatment for 12 h at ?60 °C followed by rolling process was the finest and most uniform. By increasing cryogenic treatment duration to 12 h, the yield strength of the AZ31 magnesium alloy was enhanced by 25.8% after rolling under ?60 °C cryogenic treatment temperature. Meanwhile, a four-time increase in extension rate (3.06% to 12.31%) was attained. The tensile fracture presented a mixed-mode fracture, which is characteristic of brittle and ductile fracture mechanisms.