Deformation mechanism of Ti-15Mo aged titanium alloy under dynamic impact conditions

Abstract:

The lamellar structure of Ti-15Mo alloy was obtained by solution aging treatment. The effect of strain rate on deformation mechanism was studied by split Hopkinson pressure bar (SHPB). Combined with adiabatic temperature rise, microstructure and hardness analysis, it was shown that the flow stress curve fluctuated due to the interaction between dislocation and the second phase. Increasing the strain rate, on the one hand, causes the strain rate to strengthen; On the other hand, it promotes adiabatic heating and softening. When the alloy temperature reaches 379k, the thermal softening effect exceeds the strain hardening effect, and the deformation mode changes from uniform plastic deformation to adiabatic shear deformation. The width of adiabatic shear band increases with the increase of shear strain, and equiaxed grains are produced by subcrystalline rotation recrystallization mechanism. The interface strengthening of recrystallization leads to the hardness from high to low: mixed tissue>strip tissue>matrix tissue. Aging treatment inhibits the twinning induced plasticity (TWIP) effect, resulting in lower strain hardening ability of the alloy and deteriorating the dynamic mechanical properties of the material.

Key words:Ti-15Mo alloy; dynamic impact; strain rate; adiabatic shear; dynamic recrystallization.