Growth of ordered lamellar precipitates during nitridation of Nb-10 at.% Ti at 1300 degrees C

Growth of three morphologically distinct layers occurs during the parabolic nitridation of Nb-10 at.% Ti at 1300°C under 0.3 bar nitrogen atmosphere. The outermost layer is composed of 8-(Nb,Ti)N, the intermediate layer of ?-(Nb,Ti)2N and the innermost layer corresponds to an internal precipitation zone with ordered lamellar precipitates of ?-(Nb,Ti)2N+?-(Nb,Ti). The internal precipitation front advances with parabolic kinetics and the three layers grow by nitrogen inward diffusion. The interlamellar spacing at the precipitation front increases as the reaction time increases. The formation of the lamellar micro structure can be described as a discontinuous precipitation process and the interlamellar spacing can be considered as a measure of the distance over which lateral Nb-Ti interdiffusion occurs in the alloy.