三元Fe_62.5Cu_27.5Sn₁₀合金的快速凝固组织演变机制

夏瑱超，王伟丽，翟 薇，李志强，魏炳波

(西北工业大学 应用物理系，西安 710072)

摘 要：在自由落体条件下研究三元Fe_62.5Cu_27.5Sn₁₀合金的亚稳相分离和凝固组织形成规律。结果表明：液相分离使得合金液滴在快速凝固过程中形成2~3层壳核组织和均匀弥散组织，其相组成为α-Fe固溶体和Cu₃Sn金属间化合物相。分析液滴内部L₂(富Cu)液相的运动特征发现，温度梯度和浓度梯度所引起的Marangoni运动促进壳核组织的形成，合金液滴的最终凝固组织由冷却速率、过冷度和Marangoni运动共同决定。如果液滴直径足够小，快速冷却能够抑制液相分离，凝固组织演变为等轴枝晶形态，其相组成为α-Fe固溶体和Cu₂FeSn化合物。EDS分析显示，初生α-Fe相在快速凝固过程中发生了显著的溶质截留效应。

关键词：Fe-Cu-Sn合金；相分离；快速凝固；Marangoni运动

Microstructural evolution mechanism of rapidly solidified ternary Fe_62.5Cu_27.5Sn₁₀ alloy

XIA Zhen-chao, WANG Wei-li, ZHAI Wei, LI Zhi-qiang, WEI Bing-bo

(Department of Applied Physics, Northwestern Polytechnical University, Xi’an 710072, China)

Abstract:Liquid ternary Fe_62.5Cu_27.5Sn₁₀ alloy was rapidly solidified under free fall condition. The results show that the liquid phase separation leads to the formation of two- or three-layer core-shell structures and uniformly dispersed structures. These two types of microstructures are both composed of α-Fe and Cu₃Sn phases. According to the movement characteristics of L₂(Cu-rich) liquid phase, the thermal and solutal Marangoni migrations are the dynamic mechanisms responsible for the development of core-shell structure. The finally solidified microstructure of ternary Fe_62.5Cu_27.5Sn₁₀ alloy depends on the combined effects of cooling rate, undercooling and Marangoni migration. If the droplet diameter is sufficiently small so that its high cooling rate suppresses the liquid phase separation, the solidification microstructure evolves into the equiaxed dendrite morphology. The dendritic microstructure is composed of α-Fe solid solution and Cu₂FeSn intermetallic compound. EDS analysis reveals that α-Fe phase exhibits a remarkable solute trapping effect during containerless rapid solidification.

Key words:Fe-Cu-Sn alloy; phase separation; rapid solidification; Marangoni migration