Acta Metallurgica Sinica (English Letters) ›› 2018, Vol. 31 ›› Issue (6): 604-614.DOI: 10.1007/s40195-017-0687-z

• Orginal Article • Previous Articles     Next Articles

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

Li Xiang1, Xiao-Hua Min1(), Xin Ji2, Satoshi Emura2, Cong-Qian Cheng1, Koichi Tsuchiya2   

  1. 1 School of Materials Science and Engineering, Dalian University of Technology, Dalian 116024, China
    2 Research Center for Structural Materials, National Institute for Materials Science, 1-2-1 Sengen, Tsukuba 305-004, Japan
  • Received:2017-05-17 Revised:2017-06-19 Online:2018-06-10 Published:2018-05-31

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.

Key words: β-Type titanium alloy, Pre-cold rolling, Twinning deformation, Isothermal ω-phase, Strength-ductility