热扩散处理对Al-24%Si合金中初晶硅形态的影响

Influence of heat treatment on primary silicon morphology in Al-24%Si hypereutectic alloy

采用低于Al-Si合金共晶点温度(577℃)加热保温处理,研究过共晶Al-24%Si合金在不同的加热扩散温度和保温时间下初晶硅形态的演变。结果表明:加热扩散温度为550℃,保温时间分别为3、6、9和12 h时,随保温时间的延长,粗大块状或花瓣星状的初晶硅趋于向近球状转变,且尺寸随保温时间的延长而变得细小;当保温时间为9 h,加热扩散温度为450、510、530和550℃时,随加热扩散温度的升高,初晶硅的尺寸越细小,圆整度提高,通过选择合适的加热扩散温度和保温时间进行处理可以起到使初晶硅球化和细化的效果,从而提高合金的力学性能。

The process of heating diffusion treatment at the temperatures lower than the eutectic point 577 ℃ was employed to research the morphology evolution of primary silicon in a Al-24% Si hypereutectic alloy.The results show that when the alloy is treated at 550 ℃ for 3 h to 12 h,the large block and petal-shaped primary silicon tended to change into nearly spherical and its size became smaller with increasing the holding time.When the alloy is treated at the different temperatures of 450 ℃ to 550 ℃ for 9 h,with increase of temperature,the large primary silicon is refined and became rounder.Hence,the mechanical performance of the alloy can be improved by optimum heat treatment.