Abstract
The precipitation process of A1N in a cold worked high purity Fe-0.09A1-0.01N alloy was studied. The alloy was made from a zone refined high purity iron bar (>99.99%) and an Al-Fe alloy by embedding the latter at an interval along the specimen axis and zone refining the composite in a N2-H2 atmosphere. The alloy was subsequently quenched into ice water after solution treatment of 1 250°×1hr and cold drawn 68.6% at room temperature. The electrical resistivities of the wires, annealed isochronally and isothermally, were measured in liquid nitrogen, and the precipitates of A1N were examined by electron microscope extraction replica method. The results obtained were as follows;
1) A large decrease of the electrical resistivity was observed at the temperature range from 450°C to 620°C which was attributed to the precipitation of A1N. This temperature range was lower by about 100°C than that in the not-strained specimens.
2) The precipitation processes under about 580°C could be described as a first order reaction after a respective certain period of time, for which the activation energy of reaction was 58 Kcal/mol, which suggested that the precipitation of A1N in the cold worked matrix was controlled by the diffusion of Al in cc-iron.
3) The cubic lattice structure of A1N was occasionally observed in the early stage of precipitation, but most of the precipitates observed in the high purity specimens used here were identified to be A1N of the hexagonal lattice structure.
