Precipitation Behavior of Ti15Mo Alloy and Effects on Microstructure and Mechanical Performance

Abstract

Precipitation behaviors of Ti15Mo alloy subjected to 3, 5, 10 and 20 °C/min cooling from the β phase field were investigated, and the variation trend of the activation energy during the cooling process was analyzed with DSC measurements and the Flynn–Wall–Ozawa method. The texture and microstructure of the phase transformation in different isothermal aging conditions were analyzed with XRD and TEM. The patterns of ω and ω/α in specimens aged at 450 and 500 °C show that β → ω and β → ω/α phase transformations occur, respectively. XRD spectra and SAD patterns illustrate that the precipitates transformed during aging over 525 °C are α phase. The morphology of the precipitation indicates that the size of the α phase formed in the isothermal treatment increases with increasing aging temperature. In contrast, the intensity of the (10-11)α texture decreases with increasing aging temperature. The tensile properties and fractures were investigated to determine the correlation between phase transformation and mechanical performance. The alloy has the highest ultimate tensile strength (UTS) at 1440 MPa because the ω phases transform during aging at 450 °C. A good combination of tensile properties, with a UTS of 970 MPa and an elongation of 14.5%, was obtained in the specimen aged at 550 °C for 8 h.