Phase evolution in laser rapid forming of compositionally graded Ti-Ni alloys

A graded binary titanium-nickel alloy with a compositional gradient, from elemental Ti to Ti-23.2 at. % Ni, has been successfully deposited using laser rapid forming. A metallurgical study of the phase evolution along the compositional gradient showed that a series of phase evolutions α→ α+β→ α+β+Ti₂Ni→ β/B2 +Ti ₂Ni have occurred. Phase formation and microstructure evolution along the compositional gradient was analyzed by Scheil-Gulliver and eutectic growth models. In particular, the morphology of the β/B2 +Ti₂Ni anomalous and coupled eutectic is discussed in detail.