Fabricating functionally graded Fe–Cr–Co permanent magnetic alloys via laser powder bed fusion

Abstract

Laser powder bed fusion (LPBF) in-situ alloying technology offers the possibility to construct gradient materials with varied structures and properties. Functionally graded Fe–Cr–Co permanent magnetic alloys were fabricated by LPBF and in-situ alloying mixed powders of Fe, Cr, and Co elements. The effects of different Fe, Cr and Co contents on the microstructure, magnetic properties and hardness of Fe–Cr–Co alloys prepared by LPBF were studied. The as-built Fe–Cr–Co alloys present a single body-centered-cubic phase and have a homogeneous distribution of elements. The mechanical properties and magnetic properties of the compositionally graded sample show a gradient variation. With the increase in Cr content, the Vickers hardness of the sample increases, and the saturation magnetization of the sample decreases. The optimal magnetic properties in an isotropic state are given as coercivity ${H}_{\text{cB}}$= 21.65 kA/m, remanence ${B}_{\text{r}}$= 0.70 T and energy product ${\left(BH\right)}_{\text{max}}$= 5.35 kJ/m³, which are comparable to or higher than the reported magnetic properties in an isotropic state prepared by traditional powder metallurgy. LPBF in-situ alloying technology has the potential to further explore Fe–Cr–Co magnetic materials, such as those consisting of multiple or more constituent elements, and to maximize the compositional flexibility of magnetic materials.