1977 Volume 63 Issue 6 Pages 971-979
Ghanges in thermoelectric power and electrical resistivity during 10min/20°C isochranal annealing were observed in several quenched or cold rolled specimens of low carbon aluminum-killed steel. Annealing stages corresponding to the precipitation of metastable carbide, cementite, iron-nitride and aluminum-nitride could be followed by the thermoelectric power measurement with fairly good accuracy. In the quench-aging of the steel, a weak unidentified peak was detected around 380°C, which could not be found by the resistivity measurement. From a discussion on the abnormally high value of the ratio of thermoelectric power increment to resistivity decrement (-dS/dρ), it was postulated that the aging on heating from room temperature to-100°C immediately after cold rolling (70% reduction) was associated with dissociation of point defectnitrogen complexes to form AlN molecules. The value of (-dS/dρ) for the precipitation of iron-nitrides was estimated to be -1.8V·Ω-1cm-1deg-1. The 400-480°C stage in the isochronal annealing of the cold rolled specimen could be identified as due to pre-precipitation clustering of AlN, since the (-dS/dρ) value was approximately the same as that of the precipitation of hexagonal AlN (-0.47V·Ω-1cm-1deg-1).