Comparative insights into microstructure and magnetism of Ni-Mn-Sn Heusler alloys manufactured by electron beam and laser beam powder bed fusion

Abstract

Powder bed fusion (PBF) is a promising but challenging method for additive manufacturing of magnetocaloric Ni-Mn-Sn Heusler alloys, due to the material's inherent brittleness. To produce crack-free near-net-shape parts from prealloyed gas atomized 47.2Ni-39.2Mn-13.0Sn powder, electron beam powder bed fusion (PBF-EB/M) with a stress-reducing spot melting scanning strategy was successfully employed. The same identical-sized powder was also processed using laser beam powder bed fusion (PBF-LB/M) for comparison. Notably different evaporation, microstructure, and magnetic characteristics were observed in the as-built conditions. Heat treatment at 900 °C resulted in almost fully martensitic phase structures, improved homogeneity, and increased the magnetocaloric effect, indicated by a magnetic entropy change up to 3.95 J/kg K and 2.07 J/kg K in 5 T for PBF-LB/M and PBF-EB/M processing of the alloy, respectively. These findings not only shed new light on the characteristics of PBF-processed Ni-Mn-Sn but also offer a promising approach to overcome the material's brittleness during manufacturing, enabling the production of mechanically stable magnets with improved magnetic properties.

Keywords

• Powder bed fusion
• Spot melting
• Heusler alloys
• Microstructure
• Magnetocaloric effect