Effect of Heat Treatment on Microstructure and Tensile Properties of Ti-6Al-4V Alloy Produced by Coaxial Electron Beam Wire Feeding Additive Manufacturing

A novel coaxial electron beam wire feeding additive manufacturing technology (CAEBWAM) was proposed in our previous work to refine the microstructure and improve the mechanical properties of titanium alloys. In the present work, different post-heat treatments were performed to understand the microstructure evolution and the resultant mechanical properties of CAEBWAMed Ti-6Al-4V alloy. The as-built sample was dominated by equiaxed prior beta microstructure, with the first several deposited layers containing columnar prior beta grain morphology. The as-built alloy showed a mixed microstructure composed of large alpha ' martensite and fine alpha + beta lamella. As the annealing temperature was increased, alpha ' martensite decomposed into alpha + beta phase, while the width of the alpha lamellae increased, causeing an increase in the ductility and a decrease in the strength.