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利用光学显微镜、扫描电镜、X射线衍射仪和硬度测试仪等试验手段,研究了金属型、石墨型及砂型铸造Mg-5Al-0.5Y合金分别在冷却速度为200、150和60℃/min时的微观组织和硬度的变化,并对其机理进行分析。结果表明,随着冷却速度的降低,α-Mg晶粒粗化,晶粒平均尺寸从52.83μm增大到68.96μm,增幅30.53%,而离异共晶β-Mg17Al12相从连续网状分布变为粗大的断续分布,相对含量也由10.35%减少至8.67%,降幅为16.23%;冷却速度的降低及晶粒的粗大化,还致使合金硬度也随之下降,由56.4(HV)降至51.3(HV)。
The microstructure of the as-cast Mg-5Al-0.5Y alloy was studied at different cooling rates of 200, 150 and 60 ℃ / min respectively by means of optical microscope, scanning electron microscopy, X-ray diffraction and hardness tester. The microstructure and hardness of the changes, and its mechanism analysis. The results show that as the cooling rate decreases, the α-Mg grains coarsen, the average grain size increases from 52.83μm to 68.96μm, an increase of 30.53%, and the dissimilar eutectic β-Mg17Al12 phase changes from continuous reticular distribution to Coarse and intermittent distribution, the relative content decreased from 10.35% to 8.67%, a decline of 16.23%; cooling rate decreased and the grain coarsening, also led to the alloy hardness also decreased from 56.4 (HV) to 51.3 (HV).