陶卫健, 刘海峰//金属学报.—2006；42(12).12671273 系统研究了Mg-6Al-2Sr和Mg-6Al-(1-2)Sr-1Ca合金在水冷模铸造和压铸态下的显微组织、力学及蠕变性能. Mg-6Al-2Sr合金的铸态组织由-Mg和沿枝晶界分布呈片状的-Mg+Al4Sr共晶相组成. 在Mg-6Al-2Sr基础上加入少量的Ca, 合金中的Al4Sr被Mg2Ca取代, 且出现了Mg-Al-Sr三元中间相, 合金的抗蠕变性能显著提高. 对蠕变后试样进行的扫描电镜观察表明, Mg-6Al合金中添加Sr和Ca后形成的中间相均具有很高的热稳定性. Mg-6Al-2Sr合金蠕变后的试样中出现了-Mg17Al12相的非连续析出; 而采用Sr和Ca复合合金化的试样显微组织在蠕变后无明显变化, 也未析出相, 因而显著地提高了合金的抗蠕变性能. 与水冷模铸造试样相比, 压铸试样具有更细的显微组织和更高的室温与高温力学性能, 但抗蠕变性能略低.
The microstructure, tensile and creep properties of Mg-6Al-2Sr and two Mg-6Al-(1-2)Sr-1Ca based alloys have been investigated. The results indicate that the as cast microstructure of Mg-6Al-2Sr alloy consists of the dendritic -Mg and lamellar Al4Sr intermetallics at grain boundaries. Calcium addition to Mg-6Al-2Sr alloy results in the formation of Mg2Ca compound and a Mg-Al-Sr ternary intermediate phase, and the significant improvement of creep properties. The SEM microstructure observations performed on the samples after creep tests reveal that the intermediate phases in the Mg-6Al based alloy alloys with Sr and Ca additions have high thermodynamic stability. Discontinuous precipitation of β-Mg17Al12 occurs in Mg-6Al-2Sr alloy during creep deformation, however, no obvious changes have been observed in the microstructure of the alloys with combined addition of Sr and Ca after creep tests. The die cast sample shows finer microstructure and higher room temperature and high temperature tensile properties while relatively lower creep resistance in comparison with the samples which were cast by water cooled mould.
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