Al-Si合金共晶形核与生长机制研究

Study on Eutectic Nucleation and Growth Mechanism of Al-Si alloy

Al-Si二元共晶反应发生在凝固后期,共晶(团)晶粒的形核、生长都直接影响缩松、热裂等缺陷的形成、杂质元素及化合物的分布等。对Al Si10.5亚共晶合金进行Sr变质,对未变质与变质合金进行微观组织观察和EBSD分析,并对未变质合金进行热分析。结果表明:无论变质与否,共晶在初生枝晶上形核和在枝晶间异质上形核的这两种情况都存在,并且Sr对初生α-Al有明显的变质效果,富Fe相可能对共晶Si相形核有较大影响。

Al-Si binary eutectic transformation occurs in the late solidification stage, and the nucleation, growth of eutectic （cell） crystal have direct impact on the formation of shrinkage, thermal cracking defects and the distribution of impuritiy elements and compounds. The hypoeutectic alloy A1Si10.5 was modified with Sr, and the microstmcture observation and EBSD analysis were carded out for the A1Si10.5 alloys with and without modification, and the thermal analysis of the unmodified alloy was carried out. The results show that whether the alloy with modification or not, nucleation of eutectic on primary dendrites and between dendrites exsits, and Sr has significant modification effect on the primary α-Al, and the rich Fe phase may have a great influence on the nucleation of eutectic Si phase.