Mechanical and magnetic properties of soft magnetic Fe–Ni permalloy produced by directed energy deposition processes

The present study investigated the microstructural evolutions and mechanical and magnetic properties of Fe-50%Ni (wt%) alloy fabricated by the directed energy deposition additive manufacturing process under different energy densities. The samples with high relative density (~ 97–99%) and homogeneous microstructures were successfully fabricated from the pre-alloyed Fe-50%Ni powders with an average particle of 102 μm. Mechanical properties of the printed samples were characterized via uniaxial tensile test, Vickers microhardness, and electron backscatter diffraction. The as-print microstructures contained a single FCC phase with relatively elongated grains in the building direction. The optimum sample which was produced under the highest laser power had the microhardness of ~ 167 HV, ultimate tensile strength of ~ 493 MPa, yield strength value of ~ 315 MPa, and total elongation of ~ 38.7%; thus, it was completely comparable with other Fe-based soft magnetic materials. In the case of all samples, the dislocation activity in the form of substructure development was the predominant deformation mechanism in the as-printed samples. Moreover, the highest saturation magnetization and Curie temperature of 151 emg/g, 477 °C, respectively, were achieved in the sample produced with the highest laser power and energy density; further, the lowest coercivity was 3.16 Oe obtained. The current investigation, thus, showed that a good combination of good mechanical performance and high magnetic properties could be accomplished through the DED process in the Fe-50%Ni soft magnetic permalloy by using the optimum processing condition.