中文摘要：

本文研究了熔体过热处理对过共晶Al-Si合金凝固组织的影响.实验结果发现,对合金熔体进行过热处理不仅能影响合金的形核,而且也能影响其生长.过热可使合金的初生硅细化,随过热温度的升高,合金的初生硅尺寸逐渐减小.合金液保温温度较低时,Al-19%Si合金凝固后的共晶硅为粗大的长针状,表现出小平面生长的典型特征;对合金液进行过热处理,合金凝固后的共晶硅变为细小的点状或短棒状,表现出非小平面生长的典型特征.点状和短棒状共晶硅的面积百分率随过热温度的升高和保温时间的延长而增加.

英文摘要：

Al-Si hypereutectic alloy is one of the most important casting aluminum alloys.The refinement and modification of microstructure of Al-Si hypereutectic alloy have been received great interest over the past decades.This paper deals with the effect of melt overheating treatment on the microstructure of Al-Si hypereutectic alloy.It is found that melt overheating treatment not only influences the nucleation of melt,but also influences the growth of the crystal.Melt overheating treatment can refine primary silicon of Al-Si hypereutectic alloy.The size of the primary silicon decreases with increasing the melt temperature.When the melt temperature is 800 ℃,the eutectic silicon is thin plate,which shows the feature of lateral growth.As the melt temperature increases,the eutectic silicon can transform from large plate to short rod or small point,which shows the feature of non-lateral growth.The percentage of the eutectic silicon of short rod and the small point increases with increasing the melt temperature and the holding time.