Enhancing Soft‐Magnetic Properties of Fe‐Based Nanocrystalline Materials with a Novel Double‐Scanning Technique

Abstract

This paper 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 happened during LPBF process. This technique involves double scanning where: (i) the first scan applied uses high energy density (E=P/vht, where P is laser power, v is laser scan speed, h is hatch spacing and t is layer thickness) with different process parameters (P: 30, 40 and 50 W, v: 500, 600 and 700 mm/s, h: 20 and 30 µm and t: 50 µm) to achieve high density and (ii) the second scan employed before the spreading subsequent powder layer, uses low E (= 20 J/mm3, P= 20 W, v= 1000 mm/s, h= 20 µm and t= 50 µm) to refine the microstructure and thus reduce coercivity. To comprehend microstructural change, the quantity and the particle size distribution of the α‐Fe(Si) phase (main phase in the microstructure) were measured. The double scanning strategy refined the microstructure to finer crystallites with a narrow particle size distribution. This increased the saturation magnetization (M s ) to a maximum value of 226.81 Am2/kg and reduced the coercivity (H c ) to a lowest value recorded (130 A/m). Likewise, the bulk density (94.59% ‐ 99.25%) was 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.This article is protected by copyright. All rights reserved.