挤压铸造AZ91-Ca镁合金的压缩蠕变行为

Compressive creep behavior of squeeze cast magnesium alloy AZ91-Ca

研究了温度和应力对挤压铸造AZ91-Ca合金压缩蠕变行为的影响,并对蠕变机制和微观组织演变进行了分析。研究发现:在测试温度150℃和应力50 MPa条件下,挤压铸造AZ91-Ca合金的最小蠕变速率仅为2.60×10^(-9)s^(-1),100 h后蠕变变形量仅为0.98%;在测试温度200℃和应力100 MPa条件下,最小蠕变速率达到8.93×10^(-7)s^(-1),20 h后蠕变变形量即达到12.71%。随着测试温度的升高和应力的增大,压缩蠕变过程加速,蠕变变形量和最小蠕变速率迅速升高。在测试温度200℃和应力50~100 MPa范围内,其应力指数n≈8.3,而在应力100 MPa和测试温度150~200℃范围内,其激活能Q≈124 k J。压缩蠕变过程中,二次Mg_(17)Al_(12)相不断析出。与高应力相比,高温更能促进二次Mg_(17)Al_(12)相的析出。

Effects of temperature and stress on compressive creep behavior of squeeze cast magnesium alloy AZ91-Ca were investigated,and the creep mechanism and microstructure evolution were analyzed.The results show that under temperature of 150℃and stress of 50 MPa,the minimum creep rate of AZ91-Ca alloy is only 2.60×10^-9s^-1and the creep strain after holding for 100 h is only 0.98%.When under the conditions of 200℃and 100 MPa,the minimum creep rate reaches 8.93×10^-7s^-1and the creep strain after 20 h reaches 12.71%.With the increase of testing temperature and stress,compressive creep of squeeze casting AZ91-Ca alloy accelerates,and both the minimum creep rate and creep strain increase obviously.In the stress range of 50～100 MPa and testing temperature of 200℃,the stress exponent n is about 8.3,while in the testing temperature range of 150～200℃and stress of 100 MPa,the activation energy Q is about 124 k J.During compressive creep,secondary Mg（17）Al（12）phase precipitates continuously.Compared to high stress,elevated temperature is more liable to promote the precipitation of secondary Mg（17）Al（12）phase.