Effect of travel speed and stress relief on thin Ti-6Al-4V laser wire deposits

Abstract

The effect of two travel speeds on thin Ti-6Al-4V buildups produced by Laser Wire Deposition (LWD) has been investigated. A travel speed set at 1.4 mm/s promoted recrystallization of columnar prior β grains into horizontal prior β grains. It was associated with lower strength hardly meeting minimum wrought requirements as set by the AMS4911. On the other hand, it was shown that by increasing the travel speed to 7.2 mm/s, sufficiently high cooling rates are occurring creating a fine α + β basket weave structure, while no recrystallization of the prior β grains has been observed. Tensile properties were improved with strength consistently exceeding minimum wrought requirements. An additional stress relief cycle preserved the effect of deposition parameters on material properties. A strong anisotropy in elongation was associated with the slower travel speed where higher values were derived along the Z direction. While the faster travel speed exhibited isotropic properties. Strengthening of the deposits has been observed following a stress relief cycle.