Precipitation Kinetic Analysis in a Maraging 350 Steel Using KJMA and Austin-Rickett Equations

Abstract

Maraging steels are martensitic steels hardened by intermetallic compounds that precipitate during aging heat treatments. During aging of these steels complex phenomena involving nucleation and growth of several phases as well as changes in the precipitates, morphology and stoichiometry take place. The present work aims to study the kinetics of precipitation in a maraging 350 steel through the KJMA and Austin-Rickett (AR) equations. Analysed data were obtained from Vickers microhardness measurements carried out in samples heat-treated between 440 and 560 °C. Variation in the n-constant has been observed for both equations, indicating changes in the precipitation behavior. However, the n-constant values obtained from AR equation follow the microstructural changes observed in previous works on maraging steels. Interpretation of the n-constants using the AR equation was linked to the precipitation on dislocations at 440 °C, the growth of finite long cylinders in comparison to their separation at 480 °C, and general particle growth from small dimensions at 520, and 560 °C.