Upscaling the Severe Plastic Deformation Method for the Manufacturing of Large Rare-Earth Free MnBi-Based Magnets

Abstract The magnetic rare-earth free α -MnBi phase has a high magnetic anisotropy and an increasing coercivity with increasing temperature. However, its use in practical applications is limited due to challenging manufacturing of bulk material. We introduced severe plastic deformation by high-pressure torsion as novel processing method to address this limitation. In this study, different processing parameters are evaluated and the upscaling potential of this method to obtain larger volumes of α -MnBi bulk magnets is demonstrated. The microstructural and magnetic characterization results confirm the formation of the magnetic rare-earth free α -MnBi phase in samples with a diameter of up to 30 mm. The bulk magnetic material possesses magnetic properties comparable to smaller material volumes processed with the same method.