Improvement in mechanical and magnetocaloric properties of hot-pressed La(Fe,Si)13/La70Co30 composites by grain boundary engineering

Highlights: • La(Fe,Si)₁₃/La₇₀Co₃₀ were fabricated by low temperature hot-pressing followed by annealing. • With increasing La₇₀Co₃₀ up to 16 wt%, the (σ_bc)_max improved dramatically from 63 to 352 MPa. • Co atoms from La₇₀Co₃₀ alloy diffused into the 1:13 phase, increasing the T_C of the composites. • The MCE of these composites can be adjusted by increasing La₇₀Co₃₀ and prolonging annealing time. Magnetocaloric composites La(Fe,Si)₁₃/La₇₀Co₃₀ were fabricated by hot-pressing (HP) followed by annealing. With increasing La₇₀Co₃₀ binder content up to 16 wt%, the maximum compressive strength (σ_bc)_max improved dramatically from 63 to 352 MPa. However, the maximum magnetic entropy change (–ΔS_M)_max decreased from 10.0 to 5.6 Jkg^–1K⁻¹ because of the presence of non-magnetic La₇₀Co₃₀. After annealing at 1323 K for 4 h the (σ_bc)_max of HP + Annealed composites with up to 12 wt% La₇₀Co₃₀ doubled compared to HP samples. On the other hand, for a La₇₀Co₃₀ content of 16 wt%, the (σ_bc)_max of HP + Annealed composites decreased slightly compared to that of HP samples, due to reduced α-Fe content and much greater 1:13 phase content in HP + Annealed samples. Remarkably, the (–ΔS_M)_max of HP + Annealed composites improved from 4.8 to 9.2 Jkg^–1K⁻¹ (under 2 T), due to 1:13 phase recombination, after annealing at 1323 K for 4 h.