Evolution Process of <100> Texture in Fe-Cr-Co-Mo Permanent Magnets

The present work describes the process of grain growth during secondary recrystallization, which develops the <100> texture in Fe-Cr-Co-Mo hard magnets. The secondary recrystallization was caused by heat-treating the alloys in the sequence of α, α + γ, α + γ + σ, α phase regions of Fe-Cr-Co-Mo alloys (HTSR). This heat treatment results in the development of {110}<110> textures with <100> directions aligned along the transverse direction (TD) of cold-rolled strips. The process of grain growth during secondary recrystallization can be considered as follows: (1) y and σ phases precipitate along grain boundaries and within grains by the heat treatment in α + γ and α + γ + σ region in HTSR. It results in refining the σ grains and increasing the interfacial energy of α grains. (2) the precipitated γ phase inhibits the normal grain growth of α phase and thus maintains the driving energy for secondary recrystallization. But the volume fraction of y phase decreases with increasing temperature during the last heat treatment of HTSR in α phase region. It results that the pinning effect of γ phase decreases and secondary recrystallization occurs.