Study on the oxidation and corrosion properties of titanium aluminide from a microstructural viewpoint

Abstract

Titanium Aluminide (TiAl)is increasingly becoming more attractive as a replacement to nickel superalloy in the aerospace industry due to their superior weight to strength ratio, thermal capabilities,and oxidation properties.In particular, duplexγ-TiAl andα2-Ti3Al phase seems to possess the most desirable properties for its intended use. However, existing fabrication of structural TiAl are limited to conventional casting methods, and the nature of these fabrication techniques have shown to be unsustainable in terms of economic costs and uniformity of qualitative properties. Several alternative methods of fabrication have been put forward, with powder metallurgypossessing the highest potential to overcome the short comings of casting.In this study, different ball milled samplesof the same composition was prepared, and their subsequent microstructure, corrosion,and oxidation behaviour after Spark Plasma Sintering(SPS)was investigated.Samples that were subjected to SPS with increasing ball milling parameters yielded increasing γ-TiAl phase and decreasingα2-Ti3Alphase. It appears that the samples with larger ratio of γ to α2phase tendto fare worse in oxidation and corrosion performance, and these results point towards the need of optimizing the presence of γ/α2to compromise between oxidative and mechanical properties.