Comprehensive Study\nof τ‑Phase Mn–Al–C\nMagnets: Corrosion Resistance, Structural Integrity, and Magnetic\nProperties

This study investigates the chemical, physical, and magnetic\nproperties\nof Mn–Al–C type magnets, focusing on their corrosion\nresistance. The hot compaction process is used for densification,\nproducing isotropic magnets. Microstructural analysis reveals undesirable\nfeatures, such as phase decomposition and deformation. Although these\nconsolidated magnets do not have ideal microstructural and magnetic\nproperties, they would serve as a good basis for corrosion experiments\nand provide a relative comparison of the effect on the magnetic properties.\nVoltammetry measurements compare the corrosion behavior of consolidated\nmagnets and bulk cast material, revealing a potential difference of\nabout 400 mV. The higher potential in bulk material likely results\nfrom reduced porosity and secondary phases. The formation of the β-phase\nis observed during the hot compaction process. The structural analysis\nof the corroded samples shows no substantial phase change up to 4\nweeks of exposure under different conditions. The magnetic characterization\nof the corroded samples also shows no significant differences compared\nwith the initial hot densified state. Microstructural analysis of\nthe hot-compacted τ-phase Mn–Al–C magnets shows\nnoticeable surface pitting and increased roughness under alkaline\nconditions, but no evidence of selective corrosion is observed. These\nresults suggest that Mn–Al–C alloys are promising candidates\nfor applications in which corrosion resistance is critical.