Structural Phase State, Martensitic Transformations and Inelastic Properties of TiNi-based Alloy Fabricated by Electron Beam Wire-Feed Additive Manufacturing

In this paper, the structural phase state, martensitic transformation temperatures, and inelastic properties of a TiNi-based alloy obtained by electron beam wire-feed additive manufacturing (EBAM) on a Ti49.8Ni50.2 (at %) substrate were studied. It was shown that the printed samples had an inhomogeneous coarse-grained microstructure both in the direction perpendicular and parallel to the substrate. The microstructure type of the samples obtained by EBAM depends on the distance from the substrate and is determined by the cooling conditions in the vacuum chamber of the setup for 20 h from 800°C. At room temperature, the obtained samples had a high-temperature B2-phase structure. It was established that the printed samples underwent a B2 ↔ B19' martensitic transformation upon cooling and heating. It was shown that the studied samples exhibit a superelasticity of 9.01% under torsion with an accumulated plastic strain of 1.28% (including 5.78% in the absence of plastic deformation).