Effect of Annealing on Microstructure and Magnetocaloric Properties of Plastically Deformed La0.7Ce0.3Fe13.68Mn0.2Si1.4 Alloys

In this study, we have employed a near-net-shape hot forging deformation with ∼67% reduction ratio, and an annealing process at 1223–1423 K to prepare bulk La 0.7 Ce 0.3 Fe 13.68 Mn 0.2 Si 1.4 alloys. The deformed samples are featured by a unique microstructure consisting of layered α-Fe and La-rich phases. These layered phases gradually degrade during the subsequent annealing, and eventually appear as the magnetocaloric phase (the 1:13 phase) matrix embedded mainly with the α-Fe particles. Upon annealing at 1323 K, the deformed sample has the largest 1:13 phase formation rate. Significant magnetic entropy change of 15.6 J/kg K and a relatively small magnetic hysteresis of 30.9 J/kg at 5 T are achieved in the current forged La-Ce-Fe-Mn-Si alloy on an optimal annealing condition, i.e., 1323 K for 24 h. The large magnetic entropy, rapid 1:13 phase formation rate and near-net shape make the hot-forged La-Ce-Fe-Mn-Si alloys promising magnetic refrigerants.