Extraordinary mechanical properties and room-temperature magnetocaloric effects in spark plasma sintered all-d-metal Ni-Co-Mn-Ti alloy

The all-d-metal Ni-Co-Mn-Ti Heusler alloy is a promising candidate for magnetic refrigeration application because of its considerable magnetocaloric effect and excellent mechanical properties. In this study, the influence of powder particle size on the martensitic transformation, magnetic and mechanical properties of Ni37Co13Mn34Ti16 spark plasma sintered samples have been investigated. It was found that the martensite transformation temperature was shifted to a higher value, while the mechanical properties decreased significantly with an increase in particle size. The sintered sample (S1) with a particle size of 0–15 μm exhibited enhanced characteristics such as thermal effect, magnetic and mechanical properties. The S1 martensitic transformation temperature occurred near ambient temperature, and the sample exhibited the maximum magnetic entropy changes as high as 37.53 J·kg−1·K−1 under a 5 T magnetic field. Moreover, the associated compressive fracture stress and strain were 2129 MPa and 27.78%, respectively, representing an 88.6% and 104.3% increase relative to the as-cast sample.