A study of the effects of Cu-addition on the annealing behavior and microstructures of Nd-Fe-B type sintered magnets

A high temperature homogenization treatment (1100 degrees C for one hour) is applied to sintered magnets of Nd/sub 17/Fe/sub 76.5/B/sub 5/Cu/sub 1.5/. This is followed by a low temperature anneal (600 degrees C for one hour). The magnetic properties of the samples are related to their microstructure. The formation of Nd/sub 2/Fe/sub 17/ during the homogenization and quench treatment is thought to be responsible for the fall in coercivity, and the increased remanence is attributed to an increased fraction of the Nd/sub 2/Fe/sub 14/B matrix phase. The subsequent anneal at 600 degrees C causes the disappearance of most of the Nd/sub 2/Fe/sub 17/ phase and this corresponds with an increase in the coercivity. Quenching after the 600 degrees C anneal gives better magnetic properties than slow cooling from this temperature. Furnace cooling the sample after homogenization results in the disappearance of the Nd/sub 2/Fe/sub 17/ phase and this treatment gives the highest coercivity and energy product.<
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