Enhancing soft‐magnetic properties of Fe‐based nanocrystalline materials with a novel double‐scanning technique

This article presents a novel scanning technique for the laser powder bed fusion (LPBF) of Fe-based soft-magnetic alloys, which have low glass forming ability, and microstructural change happens during LPBF process. This technique involves double scanning where 1) the first scan applied uses high energy density (E = P/vht, where P is the laser power, v is the laser scan speed, h is the hatch spacing, and t is the layer thickness) with different process parameters (P: 30, 40, and 50 W, v: 500, 600, and 700 mm s−1, h: 20 and 30 μm, and t: 50 μm) to achieve high density and 2) the second scan employed before the spreading subsequent powder layer uses low E (=20 J mm−3, P = 20 W, v = 1000 mm s−1, h = 20 μm, and t = 50 μm) to refine the microstructure and thus reduce coercivity. This increases the saturation magnetization to a maximum value of 226.81 Am2 kg−1 and reduces the coercivity to a lowest value recorded (130 A m−1). Likewise, the bulk density (94.59–99.25%) is enhanced significantly with double scanning, especially the samples produced using high P (50 W) resulting from the relieving of the mechanical and thermal stress evolving during the process.