High strength and toughness of Ti–6Al–4V sheets via cryorolling and short-period annealing

Abstract

The trade-off between strength and toughness has always been a key problem hindering the application prospect of titanium alloys. In this study, Ti–6Al–4V titanium alloy was processed by cryorolling combined with short-period vacuum annealing to overcome the problem. Results show that after annealing at 973 K, its yield strength and ultimate tensile strength were as high as 1020 MPa and 1126 MPa, respectively, and the elongation reached 10.9%. The static toughness of Ti–6Al–4V titanium alloy reached more than 12,000 MPa·%, which is the highest value compared with the rolled other kinds of titanium alloys reported in recent years. During short-period annealing of cryorolled Ti–6Al–4V sheets, the pinning effect of fine β phase particles and the competition mechanism between α and β grains inhibited the coarsening of grains. Meanwhile, partial recrystallization and recovery make the combination of micro-grains and ultrafine-grains. The shear band structure was weakened after annealing, which provides more favorable conditions for homogeneous deformation before fracture, which contributed to the enhanced toughness. The methods adopted here are suitable for large-scale industrial manufacturing the high strength and toughness Ti–6Al–4V alloys and might be applied to other kinds of Ti alloys.