Improvement of strength-ductility tradeoff in β titanium alloy through pre-strain induced twins combined with brittle ω phase

This paper provided a novel approach for improving the strength-ductility tradeoff in β titanium alloy through a combination of mechanical {332}<113> twins with brittle isothermal ω phase. Effects of pre-strain induced twins and subsequent precipitated ω phase on deformation microstructures, and tensile properties were investigated in a β-type Ti-15Mo alloy (mass%). Mechanical twins increased with increasing pre-strain from 1% to 9%, while formation of isothermal ω phase at 523-673 K for 3.6 ks was not significantly affected by the pre-strain induced twins. Yield strength and uniform elongation characteristics depended strongly on degree of pre-strain and aging temperature. An effective combination of 1-4% pre-strain and subsequent aging at 523-573 K markedly enhanced the uniform elongation in range of 8-15% at the yield strength level of 800-1000 MPa. The enhanced uniform elongation was mainly attributable to further twinning activation during deformation in conjunction with pre-strain induced twins.