Materials characterization of Ti6Al4V to NbZr1 bimetallic structure fabricated by wire arc additive manufacturing

This study investigated the microstructures and mechanical properties of a bimetallic structure (BS) of a titanium alloy (Ti6Al4V) and a niobium alloy (NbZr1) manufactured by wire arc additive manufacturing (WAAM). Three BS thin-walls were deposited with different heat input conditions: low (180 amperes (A)), medium (200 A), and high (220 A). Microstructural characterization at the interface showed that the Niobium (Nb) diffusion on the Ti6Al4V side increased as the heat input was increased. The interfacial microstructure comprised an island area and a dendritic zone with solid solutions of (& beta; Ti and Nb) and (& alpha; + & beta; Ti and Nb), respectively. The hardness ranged from 99 to 367 Vickers Hardness (HV), with a considerable decrease at the interface due to the migration of Nb. Maximum ultimate tensile strength of 567 MPa was achieved for the low heat input sample, and the failure occurred at the NbZr1 side. The fractography revealed intergranular and transgranular fracture morphologies, indicating a brittle failure. The results showed that the proposed BS has a good bonding strength, and neither defects (e.g., pores and cracks) nor intermetallic compounds were observed at the interface.