初始组织特征对充型过程中初生相演变的影响

采用电磁搅拌法制备具有不同微观初始组织特征的半固态合金熔体,利用半固态挤压铸造法铸造螺旋线试样,使用定量金相技术分析试样的初始组织、成形的螺旋线试样不同长度上的初生相微观组织特征参数(固相率、晶粒尺寸和形状因子),研究半固态合金熔体充型过程中初生相组织的演变规律.结果表明:初生固相率在充型的沿程流动过程中变化较小;初生相的晶粒尺寸、形状因子沿充型长度呈现波浪形变化,波峰和波谷出现的位置与充型长度没有明确的关系;充型后初生相晶粒尺寸的变化幅度与充型前半固态合金熔体初生相晶粒尺寸的大小有对应关系.

Effect of initial structure characteristic on evolution of primary phase in mold filling

Semi-solid alloy melt with different initial structure prepared by electromagnetic stirring method was poured into a special mold and a series of the spiral samples were obtained by semi-solid squeeze casting process. The characteristic parameters of the primary structure such as solid phase rate, grain size and shape factor of the spiral samples located at different filling length were investigated by the quantitative metallographic techniques to explore the evolution of primary phase of the semi-solid alloy melt during the mold filling. The results show that the variance of solid phase rate of primary phase is small along the path of mold filling. The grain size and shape factor vary in a wave-shape along the filling length. The positions of peak and trough of the wave have no clear relationship with the filling length. The range of variation of grain size after filling has a coincidence relation with that of primary phase before filling.