<b>Microstructure and properties of Ni-Ti-Cu alloy fabricated in situ by treble-wire arc additive manufacturing</b>

This study is the first attempt to manufactureTi50Ni45Cu5, Ti50Ni35Cu15, Ti50Ni25Cu25 alloys by treble-wire arc additive manufacturing (T-WAAM) using pure Ti, pure Ni and pure Cu wires as raw materials. The objective is to study the hysteresis of phase transformation, the microstructure evolution and properties of as-built Ni-Ti-Cu alloy. The results show that for Ti50Ni45Cu5 alloy, NiTi2, (Ni, Cu)2Ti, B2 with CsCl structure and B19′ phases are formed. For Ti50Ni35Cu15 alloy, NiTi2, B19′, Ni4Ti3, CuTi2, (Cu, Ni)Ti2 and (Cu, Ni)Ti phases are formed. For Ti50Ni25Cu25 alloy, Ti2Ni, B19′, R, (Cu, Ni)Ti, Ti2Cu, Ni4Ti3 phases are formed.With an increase of Cu content from 5 at.% to 25 at.%, the phase transition temperature increases sharply. The ultimate tensile strength of Ti50Ni45Cu5, Ti50Ni35Cu15, Ti50Ni25Cu25 are 248.2 MPa, 534.8 MPa and 261.8 MPa, respectively. Their strain is 1.71%, 6.42%, and 3.36%, respectively. For Ti50Ni45Cu5, Ti50Ni35Cu15, Ti50Ni25Cu25 alloy,the fracture mode of the Ti-Ni-Cu alloy is brittle fracture.