The second phases in Ti40 burn resistant alloy after high temperature exposure for a long time

Abstract

The Ti40 (Ti–25V–15Cr–0.2Si) alloy is a burn resistant β titanium alloy. Second phase precipitation after high temperature exposure for a long time has been studied. The second phases, i.e. Ti 5Si 3 and α, precipitate from the β matrix after the Ti40 alloy has been exposed at high temperature for a long time. The Ti 5Si 3 phase distributes discontinuously along the grain boundary if the exposure temperature is below 540°C. Exposed at 700°C for 100 h, the coarse Ti 5Si 3 phase rapidly grows, its tensile properties obviously reducing after thermal exposure when conventionally forged. Coarse Ti 5Si 3 and α phases form after exposure at 540°C for 100 h, which leads to serious decrease of tensile properties after thermal exposure for isothermally forged alloys. Ti 5Si 3 precipitates distribute discontinuously along grain boundary in the conventionally forged alloys after creep exposure. There are also many coarse rod-like α phases in isothermally forged alloys after creep exposure.