均匀化退火对超高纯AlSi1铸锭反偏析和显微组织的影响

Effect of Homogenizing Annealing on Inverse Segregation and Microstructure of Ultra-pure AlSi1 Ingot

针对超高纯AlSi1铸锭存在的Si含量反偏析现象,尝试用530℃×8h均匀化退火以降低反偏析程度。采用电感耦合等离子体发射光谱仪(ICP-OES)测量均匀化退火前后Si的质量分数,比较Si含量的变化;同时,采用光学显微镜、扫描电镜观察晶粒变化以及Si的状态、分布变化。结果表明,均匀化退火后晶粒变大,晶界连续、清晰;晶粒范围内Si固溶到基体中,重新析出呈细小均匀分布,宏观偏析(反偏析)程度有所降低,但不够明显;均匀化退火对抑制铸锭反偏析的效果并不理想。

Homogenizing annealing at 530 ℃ for 8 h was used to try to decrease the inverse segregation of Si, which exists in ultra-pure AlSil ingot. The mass fraction of Si before and after the homogenization was measured by ICP-OES, and then the change was compared. Meanwhile, the change of microstructure of crystal grains and the state and distribution of Si were investigated using OM and SEM. The results indicate that, after homogenizing annealing crystal grains become bigger, grain boundary continuous and clear. Within one grain, Si is dissolved into the matrix, and then separated out, small and well-distributed. The degree of macrosegregation （inverse segregation） decreases, but is not so evident. Homogenizing annealing does not make satisfactory effect to restrain the inverse segregation of ingots.