Effect of α phase on high-strain rate deformation behavior of laser melting deposited Ti-6.5Al-1Mo-1V-2Zr titanium alloy

Abstract

Laser melting deposition (LMD) technology enables the use of complex titanium alloy parts in ballistic applications such as lattice armors and warheads. The effect of the α phase of a LMD Ti-6.5Al-1Mo-1V-2Zr titanium alloy during compression at a high strain rate of 3000 s⁻1 was investigated. Various morphologies and textures of the α phase of the LMD alloy were obtained by annealing at different temperatures at the β transus, followed by furnace cooling. It was found that all the α phases of the annealed microstructures exhibit two fiber textures, <21̄1̄0>α and <16 0 16¯ 19>α, parallel to the building direction. The reason is that the <100>β directions of the prior-β grains were parallel to the building direction. Due to a high Schmidt factor, {101̄2} twinning occurs in the α phases with the <21̄1̄0>α fiber texture during the high-strain rate deformation. After annealing at 970 °C, the volume fraction of the α phases with the <21̄1̄0>α fiber texture increases significantly to 51.4 vol%, which leads to a significant improvement of 14.3% in the uniform ductility strain. Moreover, with an increase in the annealing temperature from 930 °C to 970 °C, the flow strength of the sample decreases slightly by 2%.