Quantification of phase transformation kinetics of 18 wt.% Ni C250 maraging steel

Research on the kinetics of precipitate formation and austenite reversion in maraging steels has received great attention due to their importance to the properties of the alloys. In the present work, the phase transformation kinetics of an 18 wt.% Ni maraging grade C250 was investigated using differential scanning calorimetry (DSC). Based on the calorimetric data obtained at different heating rates, the kinetics of precipitate formation and austenite reversion was modeled using the Johnson–Mehl–Avrami (JMA) theory. Good agreement between the calculated transformed fraction and the experimental data from DSC measurement is demonstrated for both phase transformations. The derived JMA kinetic parameters were then used to simulate the phase transformation kinetics during isothermal ageing. Comparison between the calculated kinetics and experimental data from literature was carried out. Mechanisms for precipitate formation and austenite reversion were discussed based on the value of the kinetic parameters.