Microstructure and properties of a Ni–Ti–Cr–Mo–Nb alloy fabricated in situ by dual-wire arc additive manufacturing

A Ni–Ti–Cr–Mo–Nb wall component was fabricated for the first time by dual-wire arc additive manufacturing (in situ alloying) using TA1 and Inconel 625 welding wires as feedstock for the potential application in fields characterized by low temperature environments, such as polar research and space exploration. The microstructure and properties of the as-built component were studied. The results show the as-built component consists of NiTi (B2), Cr2Ti, and Ti2Ni phases. In the upper region, Ti2Ni phase is present as nanoparticles mainly embedded in Cr2Ti phase. Cr2Ti phase is present as long oriented strips or granular precipitates. Due to the presence of secondary Cr2Ti and Ti2Ni phases, the hardness of this component is 600–650 HV0.2. The average compression strength is ∼1970 MPa and it exhibits outstanding superelasticity with a recoverable strain of 5.5%. The austenite finish temperature is −62 °C, which indicates that Ni–Ti–Cr–Mo–Nb alloy has the superelasticity at low temperature.