A microstructure with improved thermal stability and creep resistance in a novel near-alpha titanium alloy

Abstract

A triple-microstructure with the precipitation of silicide along the α/β phase boundaries and α2 phase in the Ti-5.8Al-3Sn-5Zr-0.5Mo-1.0Nb-1.0Ta-0.4Si-0.2Er alloy was prepared for improving thermal stability and creep resistance. The alloys were forged at 1050 °C and 1000 °C followed by solution treatment at 1000 °C for 1 h and subsequent ageing at 700 °C for 5 h. The effects of α morphology and precipitation characteristics on the thermal stability and creep performance of high-temperature titanium alloy were investigated. A triple-microstructure with the participation of silicide along the α/β phase boundary and α2 phase was a promising structure with improved thermal stability and creep resistance. The plasticity loss rate was 25.0% after thermal exposure at 650 °C for 100 h due to the participation and coarsening of α2 and silicide. Meanwhile, the plastic creep strain was 0.111% during the creep deformation at 650 °C for 100 h with an applied stress of 100 MPa, which was attributed to the inhibition of silicide and α2 phase for boundary migration and dislocation slipping. Furthermore, the mutual precipitation of coarsening silicide and α2 phase inside α matrix was a significant reason for the dramatic decrease in the thermal ability, which also worsened the inhibition for dislocation climbing of silicon element during the creep deformation.