Effect of Cu content on microstructure and properties of Ti-6Al-4V alloy fabricated by double-wire arc additive manufacturing

To solve the formation of coarse columnar beta grains from Ti-6Al-4 V parts fabricated by wire + arc additive manufacturing, this study adds Cu element for in-situ alloying, effectively suppressing the growth of columnar grains and further enhancing properties. The results show that an addition of Cu element suppresses the lateral growth of beta grains, eliminating the columnar structure of beta grains. Compared with the Ti-6Al-4 V component, the original beta grains in the Ti-6Al-4 V-10Cu component exhibit a refinement of 96 %. With an increase of Cu content, the phase structure of alpha-Ti transitions from lamellar to needle-like and eventually to equiaxed crystal structure. Moreover, as the Cu content rises, the precipitation of Ti2Cu increases, leading to precipitation strengthening and enhancing the microhardness. The average strength of the Ti-6Al-4 V-10Cu, Ti-6Al-4 V-11.7Cu, and Ti-6Al-4 V15.7Cu walls is increased by 35.5 %, 56.9 %, and 71.6 %, respectively, compared with the Ti-6Al-4 V wall. The ultimate tensile strength is enhanced by 34.9 %, 49.5 %, and -1.4 %, respectively. However, the elongation is reduced by 48.6 %, 63.2 %, and 75.6 %, respectively.