Unique layered microstructure and magnetocaloric effect in hot-rolled La-Fe-Co-Si plates

[Display omitted] •La-Fe-Co-Si plates were successfully produced by hot rolling at 1273 K with a reduction ratio of 31%.•Unique layered microstructure was observed in the as-rolled plates.•Dense grain boundaries formed due to the continuous recrystallization during rolling.•A significant adiabatic temperature change of 1.6 K at 1.3 T was obtained in the hot-rolled sample. Aiming to improve the heat transfer efficiency in active magnetic regeneration, this work for the first time has proposed hot rolling as a near-net-shape and up-scaled processing method to fabricate La-Fe-Si-based magnetocaloric plates. The composition of LaFe11Co0.8Si1.2 alloys was rolled at 1273 K into 2 mm thickness with a reduction ratio of 31.0%. We observed a unique layered microstructure in the hot-rolled plate: there were apparent cracks and oxidation phenomenon occurred in the part close to the plate surface, but almost defects-free deformed microstructure in the inner part. Upon the homogenization annealing, the plate has a large magnetic entropy change of 6.1 J/kg K under an applied field change of 2 T around room temperature. Additionally, by using a self-developed infrared characterization technique we directly measured a reversible adiabatic temperature change of 1.6 K in 0–1.3 T field cycles.