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 (ΔS) 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 ΔS_max 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 ΔS with highest compressive mechanical stress value of 90 MPa. A microchannel block sample was built using the optimum condition, which shows ΔS_max value of 4.2 J/kg K with adiabatic temperature change of 1.4 K at µ0H = 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.