Abstract:In the paper Laser Additive Manufacturing (LAM) has been employed to fabricate repaired samples with wrought Ti6Al4V as the substrate and Ti6Al4V (Ti64) powders with low oxygen (O≤0.13wt%) as the cladding materials. The microstructure and mechanical properties of Ti64 samples fabricated by LAM and wrought billet were investigated comparatively. The results show that the macrostructure of the laser repaired sample can be divided into three domains, including wrought substrate zone (SZ), heat affected zone (HAZ) and laser deposited zone (LDZ). The LDZ microhardness is equal to that of the SZ basically. And the HAZ microhardness is higher than both the LDZ and SZ slightly. The results of room temperature tensile test show that the strength and ductility of the wrought sample are slightly higher than the laser repaired samples. Meanwhile, the strength of the laser repaired specimen with repair ratio of 40%(i.e. area fraction of the LDZ on the transverse section of tensile sample within gauge part is 40%)is slightly lower than that of 50% repaired specimen, but the ductility is higher than the latter. Therefore it is favorable to match the strength and ductility of the wrought substrate with the LDZ with low oxygen Ti64 powders as the cladding materials, so as to improve the comprehensive properties of laser repaired Ti64 alloy. The wrought specimen tensile fracture presents a typical ductile characterization, and the repaired specimenshows a complex fractography. From the LDZ to the SZ, the tensile fracture presents a successive transformation from cleavage step to dimple fracture. It can be seen that there is a good corresponding relationship between the fracture morphology and the microstructure of the tensile samples.