Structure and magnetic study of Ni-Mn-Ga/Al composite with modified magnetocaloric properties and enhanced thermal conductivity

Abstract Magnetocaloric materials undergoing first order phase transition are important candidates for solid-state refrigeration but their narrow temperature range and noteworthy hysteresis are barriers to practical applications. To address these issues, we used hot pressing technique to prepare a metal matrix composite by choosing ball milled and heat-treated Ni-Mn-Ga particles together with Al powders (25 vol.%). Microstructure, morphology, structural transformation, thermal conductivity, magnetic and magnetocaloric properties of the prepared Ni-Mn-Ga/Al composite were systematically characterized and studied. Unlike the pure Ni-Mn-Ga bulk alloy counterparts, the composite exhibited broadened working temperature range of 120 K. Meanwhile, it possessed largely reduced hysteresis during thermal and magnetic cycling due to second order phase transition revealed by Banerjee criterion and field dependent exponent n. The composite also exhibited improved thermal conductivity of 6.7 W/mK due to decreased interface thermal resistance between Ni-Mn-Ga particles and Al matrix.