以TiAl-8.5Nb预合金粉末为原料,添加1%Sn (原子分数)粉为强化烧结剂,采用无压烧结技术制备了高致密度的高铌TiAl合金,探究了Sn添加对TiAl基合金的烧结致密化过程、微观组织和力学性能的影响规律。研究表明：添加1%Sn可降低高铌TiAl合金粉末的烧结致密化温度,提高烧结坯的致密度及线性收缩率,从而有利于降低合金组织晶粒度,改善合金综合性能。添加Sn后,合金粉末经1500 ℃烧结2 h,其致密度可达到99.1%,线收缩率达到9.3%;合金显微组织为均匀细小的α₂/γ全片层结构,片层团尺寸为40~60 μm;Sn主要固溶于γ相中,使其轴比c/a及晶胞体积增大;所制备合金的Rockwell硬度为50.1 HRC,抗压强度为2938 MPa,屈服强度为680 MPa,压缩率为29.1%,其性能指标均高于未掺杂Sn元素的高铌TiAl基合金。

High Nb containing TiAl alloys (TiAl-Nb) are a new generation of materials for high temperature structural applications because of their low density, high strength and corrosion resistance at elevated temperatures. The alloys can be processed by powder metallurgy (PM) which have more advantages including low cost-effectiveness, near net forming for complex parts with fine grain size and uniform microstructure. However, the alloy powders are difficult to achieve full densification due to their lower sintering activity, which impairs the mechanical performance of sintered parts. The present work focuses on the densification performance of TiAl-Nb alloy powders with 1%Sn (atomic fraction) as sintering aids.The effects of Sn addition on the sintering densification process, microstructure and mechanical properties of sintered alloys were investigated. The results show that 1%Sn addition can significantly reduce the sintering densification temperature of alloy powders, and increase the relative density and linear shrinkage of sintered parts. This contributes to control microstructure grain size and improve the comprehensive properties. Sintered with 1500 ℃ for 2 h, 1%Sn containing TiAl-Nb base alloys show the best densification performance, with the relative density of 99.1% and linear shrinkage of 9.3%. The alloy samples exhibit fine and uniform full lamellar microstructure, and α₂/γ lamellar colonies are sized about 40~60 μm. Sn mainly dissolved into γ phase, leading to the enhancement of axial ratio c/a and unit cell volume. The sintered TiAl-Nb-1Sn samples have been found to possess superior room-temperature mechanical properties, with a Rockwell hardness of 50.1 HRC, a compressive strength of 2938 MPa, a yield strength of 680 MPa, and a compression ratio of 29.1%, which is obviously higher than those of TiAl-Nb alloys.