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采用落管无容器处理技术实现了三元Al-32.7%Ti-11.4%Fe合金的快速凝固,获得的最大过冷度达到352 K(0.21TL)。当合金液滴直径大于300μm时,其凝固过程中发生了L→TiAl3(1 627 K)和L2→Al3Fe0.25Ti0.75(1 340 K)两次相变,凝固组织表现为少量的片状Al3Fe0.25Ti0.75相分布在初生TiAl3相枝晶间隙内。当直径减小至300μm以下时,合金液滴已具有相当大的冷却速率和过冷度,初生TiAl3相生长十分迅速,Al3Fe0.25Ti0.75相来不及形核合金液滴就已经完全凝固,凝固组织中仅有TiAl3相单相枝晶。初生TiAl3相在快速生长过程中发生了显著的溶质截留效应,其中Fe的溶质含量明显高于平衡条件下的情况,且随合金粒径的减小呈现出增大趋势。
The rapid solidification of ternary Al-32.7% Ti-11.4% Fe alloy was achieved by using the tubeless vesselless processing technology, and the maximum undercooling reached 352 K (0.21TL). When the droplet diameter of the alloy is more than 300μm, the transformation of L → TiAl3 (1 627 K) and L2 → Al3Fe0.25Ti0.75 (1 340 K) takes place during solidification, and the solidified microstructure shows a small amount of flaky Al3Fe0 .25Ti0.75 phase distribution in the primary TiAl3 phase dendrite gap. When the diameter is reduced to below 300μm, the alloy droplets have a considerable cooling rate and supercooling degree, the growth of the primary TiAl3 phase is very rapid, Al3Fe0.25Ti0.75 phase has not completely solidified alloy droplets, solidified tissue In only TiAl3 single phase dendrite. The primary TiAl3 phase has a significant solute retention effect during rapid growth. The solute content of Fe is obviously higher than that under equilibrium condition, and shows an increasing trend with the decrease of alloy particle size.