Reaction Synthesis of Gamma Titanium Aluminides at Moderate Pressures

摘要

The gamma-titanium aluminides belong to the class of ordered intermetaliics, which are in the advanced stage of development for high temperature aerospace applications. However, these aluminides suffer from low ambient ductility and toughness. The processing of gamma-aluminides through conventional ingot metallurgy (IM) route poses challenges of elemental segregation, elemental loss, non-homogenous structures, cracking and necessity of secondary mechanical working to produce useful parts. The Reaction Synthesis (RS) is a simple low-energy technique where simultaneous formation of the compound along with densification occurs and use of very small pressures can result in dense near-net-shape (NNS) products. There is no reported work on RS of Ti-48Al-2Cr-2Nb (At percent) gamma alloy, which is the most important alloy in this class of materials. The present work is on the study of basic process of RS from elemental powders of binary Ti-48Al composition followed by synthesis of ternary Ti-48Al-2Cr and quaternary Ti-48Al-2Cr-2Nb aluminides. The aluminides processed through RS technique are characterised for densification and phases present and strength retention up to 1073K is demonstrated for the homogenised quaternary aluminide. An attempt is also made to correlate the hardness to arnbient tensile strength achieved in RS binary, ternary and quaternary aluminides produced in the present study.