硅相形态及含量对Al-Si合金线膨胀系数的影响

利用金相显微镜、DIL402C高温膨胀仪等对Al-Si合金的线膨胀进行了研究。结果表明：对于Al-Si合金,硅含量越高,其线膨胀系数越小,随温度变化幅度减小;随着温度升高,磷变质比锶变质的线膨胀系数变化幅度小,合金更加稳定;此外,T6热处理也显著降低Al-Si合金的线膨胀系数。通过对合金线膨胀系数和微观组织的对比观察发现：硅相的形态和体积分数对Al-Si合金的线膨胀系数产生重要影响。初晶硅体积分数的增加和初晶硅的析出能够显著降低Al-Si合金的线膨胀系数,共晶硅的形态对合金线膨胀系数也有一定的影响,共晶硅为短棒状、颗粒状时（尤其经热处理后）,合金的线膨胀系数也显著降低。

Influence of morphology and content of silicon phase on CTE of Al-Si alloys

The linear coefficient of thermal expansion(CTE) of Al-Si alloys was studied by using Hi-scope video microscope and DIL 402C high temperature dilatometer.The results reveal that the CTE of Al-Si alloys decreases with increasing Si level.Compared with Sr modification,the Al-Si alloy modified with P has a lower CTE and is more stabilized.Moreover,T6 heat treatment can also decrease the CTE of Al-Si alloys,and improve the stability during heating-up.According to the contrasts above and combined with microstructure observation,it is found that Si phase has important influence on CTE of Al-Si alloys.The increase of volume fraction and precipitation of primary Si both can decrease the CTE.Also,eutectic Si exerts certain influence on the CTE of Al-Si alloys,i.e.the CTE decreases when eutectic Si exhibits morphology of short-bar shape and small particles,especially after heat treatment.