In-situ synchrotron X-ray diffraction analysis of the elastic behaviour of martensite and H-phase in a NiTiHf high temperature shape memory alloy fabricated by laser powder bed fusion

Abstract

• In-situ macroscopic elastic behaviour of a dual phase NiTiHf high temperature alloy obtained by laser powder bed fusion was studied. • Anisotropic behaviour of martensite is evidenced. • The micromechanical behaviour of H-phase, a strengthening phase, is shown for the first time. High temperature shape memory alloys of the Ni-Ti-Hf system are potential candidates for aerospace applications where powder bed additive manufacturing technologies are being increasingly used. In this work, a Ti-rich NiTiHf high temperature shape memory alloy powder was processed by laser powder bed fusion. The standard heat treatment of 550 ⁰C for 3 hours was imposed to promote H-phase precipitation. At room temperature, the material has a dual-phase microstructure composed of martensite, the matrix, and H-phase, as a strengthening precipitate. High energy synchrotron X-ray diffraction is used to evaluate, in-situ, the elastic behaviour of the fabricated part. The deformation anisotropy of several (h k l) families of planes of both phases is evidenced. No major texture changes were observed upon macroscopic elastic loading. We illustrate the potential of using high energy synchrotron X-ray diffraction for detailed analyses of minority phases in additively manufactured components.