Failure analysis of Sm2Co17 type permanent magnet for high temperature
With the increasing using temperature, the magnetic performance of high temperature stable Sm2Co17 type permanent magnet will be decreased. In order to explore the effect of the high temperature on microstructure of the alloy, the differential thermal analysis (DTA) was made and three distinct phase transformation temperature 254 °C, 342 °C and 540 °C were obtained. Then X-ray diffraction (XRD), scanning electron microscopy (SEM) and X-ray energy dispersive spectrometer equipped (EDS) were used to analyze the phase information, microstructure and composition of the samples treated at the above temperatures. The results suggested that the oxidation and precipitation of Cu and Fe are the key reason to result in the failure of the material, which provides an important reference for the research of the magnet.
Temperature dependence of coercivity and magnetization reversal mechanism in Sm(Co/sub bal/Fe/sub 0.1/Cu/sub y/Zr/sub 0.04/)/sub 7.0/ magnets
The temperature dependence of coercivity in Sm(Co/sub bal/Fe/sub 0.1/Cu/sub y/Zr/sub 0.04/)/sub 7.0/ magnets with y=0 to 0.20 has been systematically studied. Two models are discussed with respect to the temperature dependence of coercivity. One model considers only domain wall (DW) pinning and explains the "abnormal" behavior as a temperature-induced transition from a repulsive DW pinning to an attractive one. The other model assumes a combination of pinning and nucleation of DWs in magnetically isolated 2:17 cells. In this model, the cell-boundary pinning of DWs takes place in the alloys with low Cu content at temperatures below the Curie temperature of 1:5 phase. Nucleation controls the magnetization reversal in the case of complete magnetic isolation of the 2:17 cells. This condition is expected to be fulfilled at any temperature above RT in the Cu-rich magnets, and only above Curie temperature of the 1:5 phase in the alloys with lower Cu content.
Coercivity of precipitation hardened cobalt rare earth 17:2 permanent magnets
Abstract The influence of the microstructure on the coercivity has been investigated by means of transmission electron microscopy. It is shown that a thin coherent (CoCu) 5 Sm-cell boumdary phase, separating cells of 17:2-crystal structure, acts as a pinning centre for magnetic domain walls. The attractive interaction force is interpreted in terms of a micromagnetic theory for domain wall pinning. The coercive force is determined by the domain wall energy gradient and by the magnetoelastic coupling energy between domain wall stresses and lattice deformation strains. The calculated coercive force due to the lattice mismatch, originated by the cellular coherent precipitation structure, is comparable to the experimentally obtained values.