Magnetostrictive strain-sensitivity synergy for laser-beam powder bed fusion processed Fe81Ga19 alloys by magnetic field annealing

Abstract

Magnetostrictive Fe–Ga alloys have been demonstrated potentialities for numerous applications, whereas, suffering a tradeoff between large magnetostrictive strain and high sensitivity. Herein, bulk polycrystalline Fe81Ga19 alloys were prepared by laser-beam powder bed fusion (LPBF) and then annealed in magnetic field for manipulating the comprehensive magnetostrictive properties. Results indicate that <001> oriented grains are developed in the LPBF-prepared Fe81Ga19 alloys due to high temperature gradient. After magnetic field annealing (MFA), the magnetic domains within the alloys gradually transformed into well-arranged stripe domains, especially, flat and smooth 90° domains were established in the alloys annealed at 2600 Oe. As a result, the induced <001> orientation grains and 90° domains contributed to an improved effective magnetic anisotropy constant (57.053 kJ/m3), leading to an enhanced magnetostrictive strain of 92 ppm. Moreover, the MFA-treated alloys also displayed enhanced magnetostrictive sensitivity (0.097 ppm/Oe) owing to the smooth domain structures and low dislocation densities, demonstrating a fruitful strain-sensitivity synergy. In addition, good magnetostrictive dynamic response and enhanced compressive yield strength were also observed for the prepared alloys. This work demonstrates that LPBF and MFA might be an attractive strategy to resolve the tradeoff between strain and sensitivity, providing a basis for the preparation of high-performance magnetostrictive materials.