Ti和Zr的复合变质与热处理对ZA27合金显微组织的影响

Effects of Ti and Zr compound modification and heat treatment on microstructure of ZA27 alloy

对ZA27合金进行了变质处理和热处理试验。XRD分析和金相研究表明,变质处理不改变合金的相结构,但Ti和Zr的存在影响初生α-Al相凝固前沿的溶质分布和成分过冷,阻碍了树枝晶生长和二次枝晶的形成,使粗大的树枝晶变为细小的花瓣状枝晶。370℃×10 h固溶处理表明,变质处理有利于η相的均匀分布。320℃×3h和320℃×18 h退火表明,变质处理有明显的抑制共晶组织粗化的效果。

Compound modification and heat treatment experiments on ZA27 alloy were studied. The results of XRD and OM analyses show that the modification changes the morphology of primary α-Al dendrite from large branch-shape to small flower-shape without change of phase constitution. It is suggested that the existence of Ti and Zr influence the solute distributions and constitutional supercooling in the front of solidification interface and block the α-Al dendrite growth and secondary dendrite formation. The solid solution at 370 ℃ for 10 h shows that modification could improve the distribution of η-Zn in α-Al matrix. The annealing at 320 ℃ for 3 h and 18 h shows that modification could obviously restrain coarsening of eutectic structure.