Blending additions of aluminium and cobalt to Nd16Fe76B8 milled powder to produce sintered magnets

A blending process involving the mixing of powders of NdFeB and pure alumin ium and pure cobalt has been developed. This process has been shown to be a n effective and simple way of adding aluminium or cobalt and aluminium to t he composition. This allows the composition and hence properties of the fin ished magnets to be adjusted subsequent to the casting and milling of the b asic alloy. With additions of Al between 0 and 3 at%, a progressive decreas e in the remanence was observed. However, the coercivity was improved with a maximum improvement of 28% for an addition of 2 at% Al. The improved coer civity was attributed to the more uniform distribution of the grain boundar y phase. Combined additions of Al and Co again resulted in a reduction in r emanence for increased Al additions. The combined addition of Al and Co red uced the loss in coercivity observed for additions of Co alone. EDX analysi s of the grain boundaries showed the formation of Nd(Fe,Al), and Nd,(Co, Fe ), as well as an improved distribution of the grain boundary phase. (C) 200 0 Elsevier Science B.V. All rights reserved.