Study On Aging Treatment Of 2:17 Type SmCo Permanent Magnets

2:17 type SmCo permanent magnets have an important place in the field of permanent magnetic material. It has broad application in high temperature and low temperature coefficient field because of its high magnetic properties, high curie temperature, low temperature coefficient of remanence, good anti-causticity and temperature stability. Aging treatment process is the key technique to enhance properties of 2:17 type SmCo permanent magnets. In order to have a better understanding on the relationship among aging treatment process, magnetic properties and microstructure, aging process for 2:17 type SmCo alloy with same components as well as different components has been designed, and lots of experiments have been carried out and aging process factors which affect magnetic properties have been analysised by means of modern analysis including x-ray diffraction analysis (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM)and energy depressive analysis (EDA).The effects of aging process on microstructure and magnetic properties of Sm2(CoCuFeZr)17 magnets have been studied. The results of the experiments show that aging treatment has no influence on sample's density and remanence, but has great influence on intrinsic coercivity and magnetic energy products. After aging, single-phase solution decomposed to two phases, so intrinsic coercivity increased; the higher the aging temperature, the quicker the cell forming and the larger the cell size; The lamellae phase formed in high aging temperature provides channel for element diffusion in low aging temperature, so the magnetic properties increased during step aging process; cooling rate affects alloy properties, the optimal rate is 0.5癈/min for studied alloy.The microstructure of high intrinsic coercivity had been studied by use of transmission electron microscopy. The study shows: the studied magnet has cellular microstructure, the cells have rhombic 2:17 phase and they are surrounded by coherent1:5 hexagonal boundaries, hexagonal 2:17 lamellae phase superimposed on a cellular microstructure; The cell structure takes on rhombic, very thin 1.5H boundary phase equably surrounded 2:17R matrix phase, and each cell is isolate, this intact cellular microstructure is necessary to obtain high covercivity; The cell size and the element distribution are the key factor to obtain high properties.At last, the influence of component Cu and Zr on aging process has been studied. The results showed: the aging time to obtain optimal properties is shorter with higher Cu content; during the single equal-temperature aging process, the coercivity of high Zr content alloy is not sensitive to aging time, but sensitive during the dual-aging process. The more lamellae phases formed during the first aging process with higher Zr content alloy and the aging time is longer because the forming of lamellae phases affects the aging process; while, the lamellae phases provide pass for element diffusion, which accelerates the aging process and makes the coevercivity enhanced rapidly.