Effect of niobium on the directional solidification and properties of alnico alloys

The effect of niobium on the extent of columnar growth of grains and on the magnetic properties in Alnico alloys has been studied. Alloys containing 1 % Nb show maximum growth of columnar crystals. In columnar alloys, coercivity increases slowly with increasing niobium content up to approximately 1 %. With further increase in niobium, coercivity and remanence decrease. The maximum energy product (55 kJ m-3) has been obtained at 1 % Nb. Niobium addition has also been found to suppress the precipitation of the undesirable gamma phase.