Influence of mixing enthalpy on the microstructure of laser multi-layer deposited Ti-6Al-4V alloy

XRD and OM were used to study the phase constitution and solidified structure of the Ti-6Al-4V alloys prepared by laser multi-layer deposited pre-alloyed powder and blended elemental powder. It was found that the deposited layer obtained by using the pre-alloyed powder consists mainly of the epitaxial columnar grains, and the solidified structures change from the columnar grains to the equiaxed grains with increasing laser power. Meanwhile, the solidified structures of the deposited layer obtained by using the blended elemental powders change from large equiaxed grains to epitaxial columnar grains with increasing laser power from 1600 W to 2700 W. Laser scanning velocity has little effect on the morphology of the prior grains in the deposited layer obtained by using the blended elemental powders. The influence of mixing enthalpy on the structures of Ti-6Al-4V alloy was discussed also.