MICROSTRUCTURE CHARACTERISATION OF AS-CAST GAMMA-TITANIUM ALUMINIDE BASED INTERMETALLIC ALLOY

摘要

Gamma-Titanium aluminide alloys represent an important class of structural materials which, thanks to their excellent physical and mechanical properties, potentially may play an important role in the aerospace and automotive industries. According to Abdallah et al., these alloys warrant consideration due to attractive balance of properties for engineering applications where weight reduction, improved fuel consumption and high temperature efficiency are essential requirements. However, γ-based alloys suffer from inherent poor ductility and fracture toughness at room temperature that limit their practical use. In addition, Baudana et al. reported that the alloys experience severe oxidation above 800°C. Owing to these drawbacks, Zhan et al. recommended that these properties can be improved by addition of alloying elements and thermo-mechanical treatments. On the other hand, castability is essential for industrial applications as many of these alloys are synthesized by casting. Due to high melting point and reactivity of γ-based alloys at elevated temperature, casting is performed under vacuum or inert atmosphere to prevent oxygen or nitrogen pickup from air. In this study, the as-cast γ-based Ti-48Al-2Nb-0.7Cr-0.3Si intermetallic alloy is investigated in order to ascertain its feasibility for non-consumable arc button melting.