Recently, a research group led by Prof. LIU Jian at the Ningbo Institute of Materials Technology and Engineering (NIMTE) of Chinese Academy of Sciences (CAS), cooperating with researchers at Xi’an University of Architecture and Technology and Inner Mongolia Normal University, developed a feasible open-die forging approach to plastically deform La-Fe-Si alloys for magnetic refrigeration. The study was published in Acta Materialia.

The magnetic refrigeration based on the magnetocaloric effect (MCE) has showed great potential to replace traditional vapor-compression cooling solutions, thanks to its low-cost, energy-efficient and environmental-friendly properties.

La-Fe-Si alloys are the most promising magnetocaloric materials for solid state cooling. However, the intrinsic brittleness hinders the shaping of La-Fe-Si alloys into desired geometries for the applications in magnetic cooling devices, which usually leads to cracking and fracture.

To address this issue, the researchers proposed a near-net shaping method of open-die forging to prepare La-Fe-Si thin plates, by virtue of the excellent deformability of α-Fe phase.

This novel approach showed excellent advantages over sintered or composite materials in producing a full-dense microstructure, facilitating the phase formation, and maintaining large magnetocaloric effects. The developed La-Fe-Si thin plates with 0.5 mm in thickness achieved a large magnetic entropy change of 14 J/kg K and adiabatic temperature change of 5.7 K under 2 T field after short-term annealing.

In addition，a unique dual-phase microstructure, which consists of nonequiaxial 1:13 grains and α-Fe particles aligned perpendicular to the forging direction, yielded a significant anisotropic thermal conductivity in cross-plane and in-plane directions for the deformed La-Fe-Si plates.

This work would shed some light on the design of high efficient magnetic refrigerator with one-way enhanced thermal conduction, and accelerate its development towards application.

The study was supported by the National Key Research and Development Program of China (No. 2017YFB0702703) and the National Natural Science Foundation of China (No. 51971232).