【摘要】 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。更多还原

【Abstract】 Ternary Al-32.7%Ti-11.4%Fe alloy droplets were rapidly solidified in drop tube with a maximum undercooling of 352 K(0.21TL).When droplet diameter D>300 μm,two phase transitions,L→TiAl3(1 627 K) and L2→Al3Fe0.25Ti0.75(1 340 K)take place during solidification process,and the microstructure is characterized by a small amount of flaky Al3Fe0.25Ti0.75 phase distributing in the gaps of primary TiAl3 dendrites.When the diameter of droplet decreases below 300 μm,the primary TiAl3 phase grows rapidly and the droplet solidifies completely before the nucleation of Al3Fe0.25Ti0.75 phase.The solidified microstructure is only composed of TiAl3 single dendritic phase.Meanwhile,a conspicuous solute trapping effect occurs during rapid growth of the primary TiAl3 phase.The Fe content in TiAl3 phase is much higher than that in equilibrium solidification and increases remarkably with the decrease of droplet diameter.更多还原