Magnetism and Mechanical Properties of Mn_(1.28)Fe_(0.67)P_(0.48)Si_(0.52)/ Cu Composites

摘要

This paper reports the effect of Cu doping on phase structure, magnetocaloric effect and mechanical properties of the first-order phase transition material Mn_(1.28)Fe_(0.67)P_(0.48)Si_(0.52) XRD, SEM and EDS analyses show that: ⅰ) the main phase Mn_(1.28)Fe_(0.67)P_(0.48)Si_(0.52) of the composite crystallizes in the Fe_2P hexagonal structure with space group P-62m, ⅱ) most of Cu exists as a simple substance, ⅲ) small amounts of Cu and Mn form a solid solution, and ⅳ) when the mass ratio of Mn_(1.28)Fe_(0.67)P_(0.48)Si_(0.52):Cu reaches 10:x with x = 4, a (Mn,Fe)_3Si secondary phase appears. Magnetic measurements show that the decrease in saturation magnetization of Mn_(1.28)Fe_(0.67)P_(0.48)Si_(0.52) after Cu doping remains limited, the Curie temperature decreases, and the thermal hysteresis increases. The maximum isothermal entropy change becomes smaller as the Cu content increases. Under a 1.5 T external magnetic field, the maximum isothermal entropy change △S of the composite decreases rapidly from 11 J/kg-K at x = 0 to 4 J/kg-K at x = 5, while the width at half maximum of the entropy change curve gradually increases. Though the composite Vickers hardness is reduced, the compressive strength is greatly improved, so that the mechanical properties are significantly enhanced as a result of Cu doping.