Magnetocaloric effect, corrosion and mechanical properties of Mn1.05Fe0.9P0.5Si0.5Cux alloys

Abstract

To enhance the corrosion resistance and mechanical properties of magnetocaloric materials in the application of magnetic refrigeration, Cu was introduced into (Mn,Fe)2(P,Si) system. A series of Mn1.05Fe0.9P0.5Si0.5Cux (x = 0, 0.05, 0.10 and 0.15) alloys were prepared by arc-melting and subsequent copper mold suction casting method. The results show that Mn1.05Fe0.9P0.5Si0.5Cux alloys crystallized into a typical Fe2P-type main phase with hexagonal structure. In microstructure, most of Cu segregated at the grain boundaries of main phase, while a small amount of Cu entered the Fe2P structure. The precipitation of pure copper phase at the grain boundaries contribute to the improvement of corrosion and mechanical properties. The Curie temperature of Mn1.05Fe0.9P0.5Si0.5Cux alloys can be continuously tuned from 321 K to 248 K with the increase of copper contents, while the magnetic entropy changes slightly reduced. In comparison with Mn1.05Fe0.9P0.5Si0.5, the corrosion potential of Mn1.05Fe0.9P0.5Si0.5Cu0.15 increases from −0.3932 V to −0.2747 V, while the corrosion current density decreases by 63.2%, which indicates a significantly improved corrosion resistance. The nano-indentation tests also indicate that the incorporation of Cu can effectively improve the mechanical performance of these alloys. All results indicate that Mn1.05Fe0.9P0.5Si0.5Cux alloys are promising candidates for magnetic refrigeration applications.