Evolution of the microstructures, magnetic and mechanical behaviors of Co47.5Fe28.5Ni19Si3.4Al1.6 high-entropy alloy fabricated by laser powder bed fusion

Low strength and poor ductility limit the application opportunities of soft magnetic materials. Moreover, the increasing of magnetic properties is always at the expense of mechanical properties, presenting a trade-off relationship. In this study, laser powder bed fusion (LPBF) was employed to successfully fabricate Co47.5Fe28.5Ni19Si3.4Al1.6 high-entropy alloy (HEA) with excellent comprehensive properties. The evolution of the microstructures of the alloy, as well as the magnetic and mechanical behaviors produced with different process parameters, were systematically studied. The results showed that the microstructures of the alloy contained high-density dislocations and some Al-rich precipitates, forming unique dislocation-precipitation frameworks. In this study's comparison results, it was found that the alloy produced with 200 W, 800 mm/s in LPBF had the optimum comprehensive properties, with the saturation magnetic induction Bs, coercivity Hc, and maximum permeability μmax determined to be 1.479 T, 188.3 A/m, and 1171.8, respectively. The tensile yield strength and elongation were 417.0 MPa and 33.9%, respectively. Furthermore, the finite element simulation results revealed that the alloy had undergone multi-stage thermal cycling during LPBF. The favorable magnetic properties were ascribed to high concentration levels of ferromagnetic elements and uniform compositions. Meanwhile, the dislocation-precipitate frameworks were the main source of the excellent mechanical properties. The formations of dislocation networks were caused by the tension-compression cycles, and the appearances of precipitates were induced by the dislocations and thermal cycling processes. The present research findings provide a new strategy for the future development of high-performance soft magnetic materials.