初始Si含量对离心法制备过共晶Al-Si合金FGM中初晶硅分布的影响

很多实验表明,Si含量不同导致离心法制备过共晶Al-Si合金梯度功能材料(FGM)中初晶硅分布内外侧不同。为了解释这一实验现象,通过理论分析,提出存在一临界初始含量和临界析出温度的观点。分析表明:当Si含量低于临界含量和析出温度低于临界析出温度时,过共晶Al-Si合金析出的初晶硅密度小于残余合金熔液密度;当Si含量高于临界含量时,在临界温度以上合金析出的初晶硅密度大于合金熔液密度,临界温度以下合金析出的初晶硅密度小于合金熔液密度。这导致了离心法制备不同初始Si含量的过共晶Al-Si合金FGM中初晶硅分布于内外侧不同。最后采用实验进行了验证。

INFLUENCE OF PRIMARY Si CONTENT ON PRIMARY CRYSTAL SILICON DISTRIBUTION IN HYPEREUTECTIC Al-Si ALLOY FGM PREPARED BY CENTRIFUGAL CASTING

Many experimental phenomena show that the primary Si content affects the primary crystal silicon distribution in hypereutectic Al-Si alloy functionally gradient matrial (FGM) prepared by centrifugal casting. To control the distribution of the primary crystal silicon, the influence is studied. The critical primary Si content and critical temperature were gained by theoretical analysis. At the lower primary Si content or lower temperature than critical parameters, the density of the primary crystal silicon is lower than that of the remained Al-Si liquid alloy. When the primary Si content is higher than the critical content and the temperature is higher than the critical temperature, the density of the primary crystal silicon is higher than that of the remained liquid alloy. In the centrifugal force field, the primary crystal silicon in the hypereutectic Al-Si alloys, whose primary Si content is lower than the critical content, is assembled in the lining by the centrifugal force, and the primary crystal silicon in the high Si content hypereutectic Al-Si alloys, whose Si content is higher than the critical content, is assembled in outside and lining. The analysis agrees with the experiments.