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根据合金成分设计,在Mg-5Sn铸造合金中逐步添加2%Al及4%Zn(质量分数),实验结果表明,单独添加Al后,一次枝晶尺寸减小,且二次臂变的更加细密,合金的延伸率从6.6%提高到22.4%;Al和Zn复合添加后,长程枝晶转变为较为圆整的蔷薇状,在合金中生成了Mg_(32)(Al,Zn)_(49)相,合金的屈服强度和抗拉强度分别达到96和232 MPa,但延伸率则下降到14.8%.通过固溶时效处理,Mg-5Sn-4Zn-2Al合金在175℃时效24 h后达到硬度峰值83.5 HV,其晶内析出相由沿[0001]晶向分布的MgZn_2和块状的Mg_2Sn相组成,对应的室温屈服和抗拉强度分别提升到144和264 MPa;在150℃下其屈服强度仍可达到138 MPa,这表明合金的晶内析出的MgZn_2和Mg_2Sn相在高温下仍具有良好的强化作用.
According to the alloy composition design, 2% Al and 4% Zn were gradually added into the Mg-5Sn cast alloy. The experimental results show that after single addition of Al, the primary dendrite size decreases and the secondary arm becomes finer , The elongation of the alloy increased from 6.6% to 22.4%. After the addition of Al and Zn, the long-range dendrite transformed into a more rounded rosette, and Mg_ (32) (Al, Zn) Phase, the yield strength and tensile strength of the alloy reached 96 and 232 MPa respectively, but the elongation decreased to 14.8% .After solution aging treatment, the hardness of Mg-5Sn-4Zn-2Al alloy reached the peak value of hardness at 175 ℃ for 24 h 83.5 HV, the intragranular precipitates consist of MgZn_2 and massive Mg_2Sn phase distributed along the [0001] crystal orientation, and the corresponding room temperature yield strength and tensile strength increase to 144 and 264 MPa, respectively. The yield strength at 150 ℃ Up to 138 MPa, which indicates that the MgZn_2 and Mg_2Sn phases precipitated in the alloy still have good strengthening effect at high temperature.