Effect of Welding Speed on Microstructure and Anisotropic Properties of Wire-Arc Additive-Manufactured Ti-6Al-4V alloy

As a significant parameter required for welding, welding speed can be used to control the grain structure during the wire-arc additive manufacture of Ti64 alloy. Herein, the prior-β grain morphology and anisotropic tensile strength were examined to investigate the impact of welding speed after hammer peening treatment. Meanwhile, SYSWELD was applied to conduct a numerical analysis of the weld pool morphology and thermal history at different welding speeds. According to the experiment results, equiaxed prior-β grains developed in the faster welding speed specimen (F) and mixture prior-β grains (equiaxed and columnar) took shape in the middle and slow welding speed specimen (M and S), which was consistent with the anisotropic property as observed in the fast welding speed specimen with lower anisotropic tensile strength than others. Meanwhile, simulation results demonstrated that a faster welding speed led to a lower temperature gradient (G) and a higher solidification rate (R) resulted in a larger number of equiaxed grains compared to the slower welding speed specimen.