Spark plasma sintering consolidation of all-d-metal Ni-Co-Mn-Ti alloys from melt-spun ribbons: magnetostructural and magnetocaloric characterization

This investigation highlights the effectiveness of Spark Plasma Sintering (SPS) for consolidating all-d-metal Ni-Co-Mn-Ti multicaloric alloys, which is significant for their potential applications. Highly dense sintered samples with a nominal composition of Ni 37.5 Co 12.5 Mn 35 Ti 15 were prepared from single-phase melt-spun ribbon flakes used as precursors. The sintered samples exhibited essentially the same elemental chemical composition and phase transformation characteristics as the precursor, as confirmed by EDS analysis, thermomagnetic analysis, and differential scanning calorimetry. The martensitic transformation (MT) in both samples occurs from a B2-type cubic ferromagnetic austenite (AST) to a five-layer modulated (5 M) monoclinic antiferromagnetic martensite (MST) without a significant change in the initial and final temperatures of the structural transition. For a magnetic field change of 0–2 T, SPS samples showed a maximum magnetic-field-induced isothermal entropy change │ΔS T │ max of 8.6 J∙kg −1 ∙K −1 for the MST to AST transformation, which is comparable to that reported by other authors. • High-temperature thermal annealing is not required to obtain a single-phase material. • The highly dense sintered samples preserved the main properties associated with the magnetocaloric effect. • The average hysteresis loss <HL> at 2 T within the δ T FWHM interval is lower than the precursor ribbons