HOMOGENIZATION BEHAVIOR OF ND2(FE0.98NB0.02)14B ALLOY

The effects of the homogenisation conditions on the microstructure of a Nd2(Fe0.98Nb0.02)14B alloy have been investigated. In the as cast co ndition the microstructure of the alloy contains four phases, the Nd2F e14B matrix phase, a Nb-containing ternary phase (Nb26Fe32B42), Nd-ric h regions nd free iron. In contrast, the homogenised alloy contains on ly the first two phases and very small amounts of the Nd-rich phase. T he Nb26Fe32B42 ternary phase was found to originate (nucleate) in the heart of the free iron phase which provides strong evidence for the ro le of Nb in the removal of free iron from the microstructure. The elec trical resistivity of the alloy was measured at regular intervals duri ng the homogenisation process at 1000-degrees-C and these studies reve aled that, after 40 hours, the alloy was completely homogenised and th is was ln a good agreement with the microstructural studies. The resis tance measurements also indicated a degree of anisotropy in the as-cas t material and there was a maximum in resistance at an intermediate st age which could indicate an age hardening process. The maximum resista nce was round to correspond to a maximum microhardness value.