Hydrogen decrepitation of a 2/17 sintered magnet at room temperature

This paper reports the room temperature hydrogen decrepitation (HD) of fully dense, 2/17-type sintered magnets based on the composition, Sm(Co0.69Fe0.21Cu0.068Zr0.019)(7.49). These magnets absorb significant amounts of hydrogen over an extended period (similar to 48 h) at room temperature and at a pressure of 10 bar to give a final hydrogen uptake of 0.23 wt%. The consequence of this is the formation of a flake-like powder formed as a result of an "onion-skin" decrepitation process in these magnets. Magnetic measurements indicate that both the remanence, (Br) and the coercivity (Hcj) decrease as a result of the dissolved hydrogen and the magnetic properties are fully restored by vacuum degassing between 150 and 300 degrees C. Heating to higher temperatures result in a permanent reduction in the magnetic properties which is ascribed to changes from the optimum microstructure. It is proposed that the HD-process could be employed in the recycling of these magnets. (c) 2006 Elsevier B.V. All rights reserved.