Microstructure, magnetocaloric and mechanical properties of LaFe_11.8Si_1.2/Y₆₄Co₃₆ composites prepared by hot pressing and diffusion annealing

To elucidate the role of elements in the increase of 1:13 phase content in La-Fe-Si/RE-Co composites prepared by hot pressing and annealing, the diffusion behavior of Y and Co during annealing and their influence on the microstructure, magnetocaloric and mechanical properties of LaFe_11.8Si_1.2/ Y₆₄Co₃₆ composites were investigated. After annealing, Co atoms diffused into the LaFe_11.8Si_1.2 particles and stabilized the 1:13 phase. Y atoms reacted with Fe atoms to form the stable Y₂Fe₁₇-type phase, instead of diffusing into the 1:13 phase. As a result, the values of T _C and (− ΔS _M)^max increased. A relatively large (− ΔS _M)^max of 4.94 J/(kg·K) (μ ₀∆H = 2 T) at a T _C of ~ 223 K was observed. Y₂Fe₁₇-type phase bonded with the LaFe_11.8Si_1.2 particles, resulting in improved compressive strength (σ _bc)^max of 309 MPa for a Y₆₄Co₃₆ content of 10wt%. Graphical abstract: [Figure not available: see fulltext.] (a) Schematic diagram of synthesis of LaFe_11.8Si_1.2/xwt%Y₆₄Co₃₆ bulk composites and element diffusion; (b) Relatively large magnetic entropy changes of LaFe_11.8Si_1.2/xwt%Y₆₄Co₃₆ HT bulk composites; (c) The excellent mechanical properties of LaFe_11.8Si_1.2/xwt%Y₆₄Co₃₆ HT bulk composites.