Novel eutectoid Ti-5Ni alloy fabricated via direct energy deposition

Abstract Direct energy deposited (DED) Ti-5Ni (wt.%) alloys promote significant grain refinement with fine equiaxed grains (~30–50 μm); they have discontinuous grain boundary α, fine eutectoid α laths (~1 μm width), and α + Ti2Ni phases. Post-heat treatment below beta transus for 24 h stimulates the formation of near equiaxed α, and the temperature significantly influenced the microstructural constituents, which included pre-eutectoid α + retained β + Ti2Ni (760°C), pre-eutectoid α + α’ + Ti2Ni (800°C), and fully α’ + Ti2Ni (850°C) phases. The tensile properties of the as-fabricated and the heat-treated alloy remarkably improved compared with the other conventionally processed eutectoid Ti-Ni binary alloys. Thus, the proposed approach opens up new opportunities and possibilities for fabricating other eutectoid-forming alloy systems with improved manufacturing efficiency, which can overcome limitations in the other manufacturing processes.