LaFe13−xSixHz magnetocaloric composites obtained via room temperature processing

Abstract

LaFe13−xSixHz alloys are promising candidates for room temperature magnetic refrigeration, but their brittle behaviour hinders their shaping into magnetocaloric devices. Metal bonding of LaFe13−xSixHz particles has been performed to overcome this issue, but the fabrication processes reported so far involve the exposure of LaFe13−xSixHz particles to temperatures where dehydrogenation occurs, which deteriorates their magnetocaloric properties. This work proposes two processing routes (P1 and P2) which were carried out entirely at room temperature, hence avoiding dehydrogenation. Route P1 consisted of binding LaFe13−xSixHz particles with Sn, while in route P2 two binders were combined: Sn and Cu. Final average porosities were equal to 12.8 % (P1) and 12.1 % (P2), which are comparable to what has been reported for hot processed composites, and differential scanning calorimetry analyses indicated that dehydrogenation did not occur during processing, an improvement in comparison to hot processing. Complementarily, the mechanical behaviour of the composites was investigated via Weibull analysis. Characteristic strengths of 49.9 MPa (P1) and 60.7 MPa (P2) were found under uniaxial compression, showing that the combination of Cu and Sn as binders promoted higher strength. Weibull moduli of 10.9 (P1) and 8.8 (P2) were identified, which are greater than what has been previously reported for a bulk alloy, indicating that embedding LaFe13−xSixHz particles in a metallic matrix led to a less brittle-like behaviour.