Abstract
Owing to the high temperature stability of hysteretic characteristics and corrosion resistance under external actions, (Sm,Zr)(Co,Cu,Fe)z-based magnets are widely used in devices operating at high temperatures, most critical constructions of aerospace engineering and defense technology, and in traction electric motors for transport engineering. A number of modern 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 as-cast state and after heat treatment, which includes the solid solution treatment at 1150 – 1180 °С for 5 h, subsequent water quenching, isothermal aging at 800 °С for 20 h, and cooling (stepped aging) from 800 to 400 °С at an average cooling rate of 100 °С/h. The results obtained allowed us to suggest the schematic diagram of grain-boundary constituent transformation at different stages of heat treatment of (Sm,Zr)(Co,Cu,Fe)z permanent magnets prepared by powder metallurgy. The formation mechanism of high-coercivity state of (Sm,Zr)(Co,Cu,Fe)z permanent magnets in the course of complete heat treatment cycle is given as the sequence of phase transformations accompanied by redistribution of a number of alloy components.
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