Abstract
Precipitation hardening in an Fe–12Ni–6Mn maraging steel during overaging was quantified in the current work. Based on hardness measurements, the precipitate size was calculated as a function of time and temperature by applying the Ashby–Orowan relationship. The commonly used Lifshitz–Slyozov–Wagner (LSW) relationship was revised by taking into account the progress of precipitate fraction during overaging. Calculated hardness results based on the revised LSW model agree very well with experimental observations. Diffusion coefficients that control precipitate coarsening during overaging were calculated and were much higher than those for aging period. This seems to imply that precipitate growth during aging and coarsening during overaging are not controlled by the same diffusion mechanism. A combination of the current work with the authors’ previous model for underaging period can describe the entire process of precipitation hardening during aging. These models are based on well recognised physical metallurgical theories and therefore can be applied to any precipitation hardening material.
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