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采用半固态等温热处理法研究了0.5wt%Y变质SiCP/AZ61复合材料的组织演变过程。结果表明,本试验中变质后SiCP/AZ61复合材料最佳半固态组织的制备工艺条件为:加热温度595～600℃、保温30～60 min。与未变质SiCP/AZ61复合材料相比,0.5wt%Y变质SiCP/AZ61复合材料的粗化速率常数较小,具有较好的热稳定性;加热温度高于605℃时,0.5wt%Y变质SiCP/AZ61复合材料中液相体积分数较高,试样出现严重变形和流淌,不能满足后续触变成形时的组织要求。在整个半固态等温热处理过程中,0.5wt%Y变质SiCP/AZ61复合材料组织的演化机制主要体现为:枝晶臂及晶粒间熔合合并→β相熔化晶界分离→晶粒组织(α-Mg)部分球化→完全球化→粗化长大。
The microstructure evolution of 0.5wt% Y modified SiCP / AZ61 composites was studied by semi-solid isothermal heat treatment. The results show that the best preparation conditions of the semi-solid SiCP / AZ61 composites are as follows: the heating temperature is 595 ~ 600 ℃ and the temperature is kept for 30 ~ 60 min. Compared with the unmodified SiCP / AZ61 composites, the 0.5wt% Y modified SiCP / AZ61 composites have smaller coarsening rate constants and better thermal stability. When the heating temperature is higher than 605 ℃, 0.5wt% Y deteriorates The SiCP / AZ61 composites have high liquid volume fraction and severe deformation and flow of the sample, which can not meet the organizational requirements of subsequent thixoforming. During the whole semi-solid isothermal heat treatment, the evolution mechanism of 0.5wt% Y-modified SiCP / AZ61 composites is mainly as follows: the dendritic arm and intergranular fusion → the β-phase melting intergranular separation → the grain structure α-Mg) partial spheroidization → complete spheroidization → coarsening and growth.