Kinetics of Precipitation from Quenched Low Carbon Steel

This paper describes new rate equations which fit exactly the experimental data of carbon precipitation from supersaturated α iron. The experimental data reported by Abe and Suzuki, electrical resistivity, thermoelectric power, and Vickers hardness, are used. A low carbon steel is quenched from 700°C and aged isothermally in the range from 35 °C to 300°C. Aging curves are separated into two curves corresponding to characteristic precipitates, and superposition of the two curves elucidates the reason why two-stage aging curves often appear. The separation of aging curves clarifies the temperature dependence of each precipitation, and activation energies of 0.57, 1.21, 0.80, and 1.45 eV are obtained for cluster, e carbide formed below 75 °C, ε carbide above 100°C, and cementite, respectively.