First-order phase transition La-Fe-Si bulk materials with small hysteresis by laser powder bed fusion: Microstructure and magnetocaloric effect

In this study, laser powder bed fusion method is used to fabricate first-order phase transition LaFe13.9Si1.4 bulk materials. The main finding is that a negligible hysteresis is obtained after annealing. We attribute this primarily to the numerous refined alpha-Fe residual phase which promotes the paramagnetic/ferromagnetic phase transition by the stray field at the interface. The fine microstructure and amorphous/nanocrystalline La-rich phase in the as-printed sample contribute to the formation of the refined alpha-Fe phases accompanied by a large alpha-Fe/La(Fe, Si)13 interface during annealing. More importantly, the first-order phase transition behavior is maintained and the magnetic entropy change for 0-2 T is 13.4 J/kg K. This study demonstrates that laser powder bed fusion is a feasible approach for fabricating high-performance rare-earth-based magnetic materials.