Formation of pure $$\tau$$-phase in Mn–Al–C by fast annealing using spark plasma sintering
Source abstract
Abstract
Abstract Mn–Al–C is intended to be one of the “gap magnets” with magnetic performance in-between ferrites and Nd-Fe-B. These magnets are based on the metastable ferromagnetic $$\tau$$-phase with L1$$_0$$ structure, which requires well controlled synthesis to prevent the formation of secondary phases, detrimental for magnetic properties. Here, we investigate the formation of $$\tau$$-phase in Mn–Al–C using Spark Plasma Sintering (SPS) and compare with conventional annealing. The effect of SPS parameters (pressure and electric current) on the phase formation is also studied. Single $$\tau$$-phase is obtained for annealing 5 min at $$500~^\circ \hbox {C}$$ with SPS. In addition, we show that the initial grain size of the $$\epsilon$$-phase is influencing the $$\tau$$-phase transformation and fraction at a given annealing condition, independently of the annealing method used. A faster transformation was observed for smaller initial $$\epsilon$$-grains. The samples obtained by SPS showed comparable magnetic properties with the conventional annealed ones, reaching coercivity of 0.18 T and saturation magnetization of 114 Am$$^2$$/kg in the optimized samples. The similarity in coercivity is related to the microstructure, as we reveal the presence of structure defects like twin boundaries and dislocations in both materials. Graphical abstract
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Research context
OpenAlex topics: Magnetic Properties of Alloys · Heusler alloys: electronic and magnetic properties · Rare-earth and actinide compounds
SciVX discovery tags are terminology-based. OpenAlex topics are source-provided classifications.
References (41)
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