The Development of a Super-alpha2 Titanium Aluminide Alloy Consolidated by Rapid Omnidirectional Compaction

Six super-alpha 2 titanium aluminide 'pancakes' were produced by rapid omnidirectional compaction of prealloyed Ti-25A1-1ONb-3V-1Mo (at%) powder. The beta-transus temperature was found to be about 1,090 deg C (1,990 deg F). The alloy was heat-treated with four different schedules to develop various structure combinations of (alpha 2 and beta, and followed by a series of microstructural analyses and mechanical property determinations. The highest ultimate tensile and yield strengths attained at room temperatures were 1,174.9 and 977.7 MPa (170.4 and 141.8 ksi), respectively. However, the elongation was less than 2%. The alloy also showed good stress rupture resistance. It was observed that, under otherwise similar conditions, ductility increased with the aspect ratio of the (alpha 2 phase but the tensile strength is inversely related to the aspect ratio. During the tensile and stress rupture tests, multiple transverse cracks nucleated in the longitudinal direction on the specimen surface and within the specimen simultaneously. Titanium aluminide, Rapid omnidirectional compaction, Fracture mechanism.