Enabling high efficiency magnetic refrigeration using laser powder bed fusion of porous LaCe(Fe,Mn,Si)13 structures

The aim of this study is to assess the processability of the LaCe(Fe,Mn,Si)13 magnetocaloric material using laser powder bed fusion (LPBF) to create room temperature high surface-area-to-volume magnetic refrigeration media. LPBF process optimisation was performed on block samples, focusing on the build densification and the microstructural development. The porosity fraction decreased with the increase in laser energy density (E), however, cracks and keyholes were induced at E >= 140 J/mm3. Following thermal heat treatment and quenching, the magnetic entropy change (Delta S) of the blocks increased with the increase in E, due to the increase in homogeneity, where the maximum value achieved at a Curie temperature (Tc) of ~290 K for the sample built using E = 123 J/mm3 was 4.9 J/kg K. Meanwhile, the samples built using E > 140 J/mm3 showed higher Delta Smax values that reaches 7.2 J/kg K but at lower Tc of 260 K and the samples are rich in cracks. The block sample built using E = 123 J/mm3 is recommended as the optimum condition, where it shows the lowest defects and the highest room temperature Delta S with highest compressive mechanical stress value of 90 MPa. A microchannel block sample was built using the optimum condition, which shows Delta Smax value of 4.2 J/kg K with adiabatic temperature change of 1.4 K at mu 0H =1 T, which is close to the value of the block sample revealing the consistency in the magnetocaloric properties between the block and the porous samples.

Automated summary

This study aims to assess the processability of LaCe(Fe,Mn,Si)13 magnetocaloric material using laser powder bed fusion (LPBF) and optimize the process parameters. The results show that increasing laser energy density can decrease the porosity fraction of the samples, but also induce cracks and keyholes. After thermal heat treatment, the magnetic entropy change of the samples increases with the increase in laser energy density, but samples built with higher energy density exhibit more cracks. The optimum condition is determined to be an energy density of 123 J/mm3, which results in the lowest defects and highest room temperature magnetic entropy change.