Single-Step Thermo-Mechano-Chemical Approach for Advance Magnet Manufacturing

Demand for strong permanent magnets has been rising due to their diverse and unique applications. Traditionally, these magnets are produced through powder metallurgy, but their inherent brittleness limits manufacturing yields. Herein, an alternative single-step method for mechano-chemical sintering of brittle Sm-Co magnetic powders through Friction Stir Consolidation (FSC) - resulting in a combination of mechano-chemo-thermal stimuli, is reported. Open-air FSC of commercially obtained SmCo ₅ (containing Sm ₂ Co ₇ ) led to oxidation of Sm ₂ Co ₇ into nano-crystalline SmCo _(5-x) (where x < 1) precipitates and Sm ₂ O ₃ phases. Heat generated due to the redox reaction and adiabatic heating abets compaction. Degree of phase transition during FSC was dependent on dwell time, with longer times facilitating transformation of Sm ₂ Co ₇ into SmCo _(5-x) and improving saturation magnetization. This study demonstrates that a low-temperature, shear-assisted deformation and consolidation process can effectively consolidate brittle powders like SmCo ₅ with concomitant reduction in total Sm ₂ Co ₇ contaminant. Our method leads to enhancement of desired magnetic properties in Sm-Co magnets by controlling the initial powder mix and processing conditions (i.e., atmosphere and process parameters) during FSC.