Rs. Mottram et al., Blending additions of aluminium and cobalt to Nd16Fe76B8 milled powder to produce sintered magnets, J MAGN MAGN, 222(3), 2000, pp. 305-313
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
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