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 aluminium and pure cobalt has been developed. This process has been shown to be an effective and simple way of adding aluminium or cobalt and aluminium to the composition. This allows the composition and hence properties of the finished magnets to be adjusted subsequent to the casting and milling of the basic alloy. With additions of Al between 0 and 3 at%, a progressive decrease 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 coercivity was attributed to the more uniform distribution of the grain boundary phase. Combined additions of Al and Co again resulted in a reduction in remanence for increased Al additions. The combined addition of Al and Co reduced the loss in coercivity observed for additions of Co alone. EDX analysis of the grain boundaries showed the formation of Nd(Fe,Al)(2) and Nd-3(Co, Fe), as well as an improved distribution of the grain boundary phase. (C) 2000 Elsevier Science B.V. All rights reserved.