Mechanism of heterogeneous phase formation induced by Ti addition in NdFeB magnets and multifactor synergistic strengthening of mechanical properties

This study demonstrates simultaneous enhancement of magnetic and mechanical properties in NdFeB magnets through Ti addition. The coercivity increases by 1.1 kOe without compromising remanence, while bending strength improves by 159.05%. Analytical results reveal that Ti predominantly combines with free B atoms to form TiB₂ phases, which reduce the brittleness of grain boundary (GB) phase and impede dislocation motion. The superposition of stress fields around dislocations generates reactive forces that counteract external loads, thereby enhancing GB strength. Concurrently, B depletion in GB phases induces amorphous transformation, further enhancing boundary strength. A minor fraction of Ti incorporates into the main phase, enhancing covalent bond strength and forming a reinforced main phase. Additionally, Ti addition promotes grain refinement and increases GB density, significantly improving bending strength. The synergistic effects of heterogeneous phase formation, amorphous transformation, main phase reinforcement, and grain refinement collectively enable coordinated strengthening between the main phase and GBs. This multi-mechanism approach provides novel insights for mechanical property optimization in NdFeB magnets.