Additive manufacturing for 3D microchannel structure using La(FexSi1-x)13 magnetic refrigerant via laser powder bed fusion

The fabrication of a three-dimensional (3D) channel/pillar structure with a submillimeter scale using La(FexSi1-x)13 magnetocaloric material was attempted via a laser powder bed fusion (LPBF) process to realize a regenerative bed for a room temperature magnetic refrigerator. The LPBF condition was found to govern not only the shaping conditions but also the metallographic structure in the as-fused state. The latter determines the quality of La(FexSi1-x)13 in the final state after annealing to homogenize the as-fused state, which has a strong impact on the magnetocaloric effect (MCE). The LPBF condition was optimized to balance the shaping and MCE performances from data science technique (i. e., the principal component analyses) by parameterizing the properties of the test specimens fabricated under varying conditions. The optimized LPBF condition enables fabrication of a 3D channel/pillar bed with magnetic entropy change of -17 J/kg K at 1T. In the active magnetic regenerator-type module, the channel/pillar bed exhibited a lower performance than the target value because the channels were clogged by the adhesion of powders to pillars due to sintering occurring below the melt pool. Ideal correction of the experimental data indicated that unclogging the channel would revive the performance superior to that of the randomly packed bed while maintaining a lower pressure drop.