在自由落体条件下研究三元 Fe62.5Cu27.5Sn10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.
@@@@Liquid ternary Fe62.5Cu27.5Sn10 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 ofα-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 Fe62.5Cu27.5Sn10 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.
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