Structure of Alloys for (Sm, Zr)(Co, Cu, Fe)z Permanent Magnets and Formation Mechanism of High-Coercivity State
摘要
Contemporary research methods are used to study in detail the structure and phase composition of the (Sm, Zr)(Co, Cu, Fe)z alloys with z = 5.5–7.0 in the as-cast state and after heat treatment, which includes the solid-solution treatment at 1150–1180°C for 5 h, subsequent water quenching, isothermal aging at 800°C for 20 h, and cooling (stepped aging) from 800 to 400°C at an average rate of 100°C/h. The transformation scheme of boundary structural constituent of a (Sm, Zr)(Co, Cu, Fe)z permanent magnet manufactured by powder metallurgy technology is proposed for different heat treatment stages. The formation mechanism of the high-coercivity state of a permanent magnet in the course of complete cycle of heat treatments is given in the form of a sequence of phase transformations accompanied by the redistribution of a number of constituents of the (Sm, Zr)(Co, Cu, Fe)z alloy.