Microstructural evolution of a new beta titanium alloy during the beta annealing, slow cooling and aging process

Abstract

A new beta titanium alloy Ti–4Al–7Mo–3Cr–3V (Ti-4733) was developed and its microstructural evolution during the Beta Annealing followed by Slow Cooling and Aging (BASCA) process was investigated. The effect of microstructure on the tensile properties was discussed and compared with the one of the commercial titanium alloy Ti-5553. The results showed that the BASCA heat treatment results in a microstructure with combination of grain boundary α and lamellar α phase colonies formed during the slow cooling and fine acicular α precipitates formed during the subsequent aging. The BASCA-processed specimens exhibited a high elongation and relatively high strength. The fracture mode in BASCA specimens was found to be a combination of ductile and transgranular brittle fracture. Although the alpha phase morphology was similar in both the alloys, the obtained microstructure was generally finer in Ti-4733 than in the Ti-5553 alloy, leading to enhanced tensile properties.