Effect of heat input on the microstructure and mechanical properties of Ti–6Al–4V alloy repaired by wire-feed electron beam additive manufacturing

Abstract

Wire-feed electron beam additive manufacturing (WFEBAM) was utilized to repair the damaged Ti6Al4V (abbreviated as Ti64) alloy with B and Y modified Ti64 wire, and the effect of heat input on the repaired microstructure and properties of Ti64 alloy was investigated. The results indicated that the sizes of prior columnar β grains and α laths increased gradually with increased heat input. Besides the fine acicular α laths, continuous αGB, and retained β phase, bits of needle-like TiB and Y2O3 nanoparticles were formed in the deposited zone (DZ) due to the addition of B and Y elements in Ti64 wire. In addition, the increased heat input reduced the microhardness and wear resistance of the DZ, while still being superior to the mechanical properties of Ti64 substrate. It is attributed to the refinement of α laths and precipitates. Compared with Ti64 substrate, the DZ in as-repaired sample 1# with the lowest heat input (288 J/mm) showed the maximum microhardness (386HV), 18% higher than that of Ti64 substrate. While the DZ 1# also obtained the lowest friction coefficient (0.49), about 80.3% of Ti64 substrate. The tensile strength and elongation of the DZ 1# were 840.6 MPa and 14%, respectively, both of which remained above 88% of Ti64 substrate. Therefore, the as-repaired sample 1# with the lowest heat input could meet the repair requirements.