Effect of Pre-cold Rolling-Induced Twins and Subsequent Precipitated ω-Phase on Mechanical Properties in a β-Type Ti–Mo Alloy

Abstract

This paper reported an effectiveness of pre-cold rolling-induced {332} < 113 > twins combined with subsequent isothermal ω-phase formation for enhancement of uniform elongation in a β-type Ti–15Mo alloy with high yield strength level. Mechanical {332} < 113 > twins were induced by cold rolling with an thickness reduction of 5%, which had little effect on ω-phase precipitation after aging at 573 K for 3.6 ks. Twinning after the cold rolling was further activated during tensile deformation, even with the presence of isothermal ω-phase. This combination of twins and ω-phase enhanced uniform elongation from 0 to 9% at yield strength level of 890 MPa. The high yield strength was mainly dominated by dislocation slip due to the isothermal ω-phase formation, and early onset of plastic instability after yielding was hindered due to the pre-cold rolling-induced twins. Dynamic microstructural refinement was induced by further twinning activation during deformation, which resulted in high work hardening rate corresponding enhancement of uniform elongation.