Influence of LPBF parameters and heat treatments on the optimization of magnetic and mechanical properties of Fe-50wt.% Ni permalloy

Details

Supervisors

Simar, Aude ; Dehez, Bruno

Faculty

Ecole polytechnique de Louvain

Degree label

Master [120] : ingénieur civil électromécanicien, à finalité spécialisée: mécatronique
Master [120] : ingénieur civil électromécanicien, à finalité spécialisée: mécatronique

Abstract

enAdditive manufacturing is increasingly used to produce complex geometries unattainable through conventional machining. Laser Powder Bed Fusion (LPBF) enables the fabrication of customized core designs that minimize energy losses and optimize magnetic flux. The Fe-50wt.% Ni alloy is promising due to its low coercivity, high magnetic permeability, and high saturation magnetization. This makes it suitable for efficient electric motors. Current literature on LPBF-processed Fe-50wt.% Ni is limited. Existing studies lack an evaluation correlating microstructural evolution with magnetic and mechanical properties, especially regarding thermal post-processing. An optimal processing window for this alloy has not been established. This study aims to characterize the density, microstructure, magnetic properties, and mechanical properties of LPBF-processed Fe-50wt.% Ni to identify optimal manufacturing parameters. Cubic samples were fabricated using different combinations of laser power and scan speed. Layer thickness and hatch spacing were kept constant to define a printability window and maximize relative density. Single scan tracks were analyzed to understand the melt pool regimes. Following microstructural characterization, ring cores and tensile specimens were manufactured to evaluate magnetic and mechanical performance in as-built and annealed states. Results show that structural and functional properties depend on the applied Linear Energy Density (LED). This dependence is governed by the interplay between defect density and microstructure. A trade-off was identified between achieving high density, magnetic performance, and mechanical integrity. Processing parameters yielding a relative density over 99% and a saturation magnetization approaching that of conventionally manufactured parts were identified. The findings show that high-temperature annealing is necessary to optimize magnetic properties. However, refining layer thickness, hatch spacing, and scanning strategy remains essential to unlock the material's full potential.