利用金相显微镜、扫描电镜、X线衍射分析和维氏硬度测试仪等手段，研究热处理工艺对Y变质的Mg-7Al合金微观组织及硬度的影响。结果表明：T4工艺处理后β-Mgl7A112相几乎全部溶入α-Mg基体中，而高熔点的稀土化合物Al2Y相在试验温度下不能分解和固溶；T6工艺处理使β-Mgl7A112相以层片状和点状共存的方式再次析出，改善了其原本粗大的网状形貌，时效温度越高，β-Mgl7A112相的层片状析出量越少，且Y的加入会抑制和推迟β-Mg17A112相的析出；Mg-7Al-xY合金最佳热处理工艺为400℃×8 h+200℃×6 h，当Y的质量分数为0.5%时，合金的硬度由铸态的62.2HV升高到时效态的85.95HV，比铸态提高了23.75%。
Effects of heat treatment on microstructure and hardness of Mg-7Al-xY magnesium alloy were investigated by the means of optical microscopy,scanning electron microscope,X ray diffraction analysis and Vivtorinox hardness tester. The results show that the net-like β-Mgl7A112 distributed along grain boundary disappears completely after T4 heat treatment,while at the test temperature,Al2Y phase with high melting point can not be decomposed. Aging after solution treatment causes the β-Mg17Al12 phase to precipitate once more in the form of layered and spotted state,which improves its original pattern of thick mesh;and the higher temperature in aging treatment,the less amount of layered β-Mg17Al12 phase can be precipitated. The precipitation behavior of theβ-Mg17Al12 phase can be restrained and delayed due to the mixing of Y. The proper heat treatment parameters of the Mg-7Al-xY alloy is 400℃for 8 h and 200℃for 6 h,when the Y content in the alloys is 0.5%,the hardness is improved from 62.2HVto 85.95HV,23.75%higher than that of as-cast.
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