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<p>This study investigates the kinetics of austenite reverse transformation during rapid heating in a low-carbon martensitic steel with fine prior austenite grains, combining experimental observations and phase field modeling. Rapid heating tests were conducted using a Gleeble 3500 thermo-mechanical simulator. Microstructure and austenite fraction were analyzed by SEM and dilatometry. EBSD analysis revealed that austenite nucleates predominantly at prior austenite grain boundaries and exhibits an austenite memory effect. A multi-phase field model has been coupled with a nucleation model to describe austenite formation from martensite. Martensite is considered as carbon-supersaturated ferrite with cementite and austenite formation assumed to occur under para-equilibrium conditions, <i>i.e.,</i> controlled by carbon diffusion. The proposed model successfully reproduces the experimental austenite transformation kinetics up to a transformed fraction of about 0.9, while deviations appear in the final transformation stage, likely reflecting mechanisms not explicitly included in the present framework, such as the diffusion of substitutional alloying elements, <i>i.e.,</i> Mn. This study provides significant insights into the rapid reverse transformation mechanism in fine-grained martensitic steels, which is crucial for predicting and controlling the properties of welded joints in ultra-high strength steels.</p>

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Austenite Reversion During Rapid Heating in a Low Carbon Martensitic Steel

  • 期刊论文

  • 发表日期：

    2026年7月28日

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  • Chikaumi Sawanishi,
  • Sabyasachi Roy,
  • Ruth Birch,
  • Matthias Militzer

摘要

This study investigates the kinetics of austenite reverse transformation during rapid heating in a low-carbon martensitic steel with fine prior austenite grains, combining experimental observations and phase field modeling. Rapid heating tests were conducted using a Gleeble 3500 thermo-mechanical simulator. Microstructure and austenite fraction were analyzed by SEM and dilatometry. EBSD analysis revealed that austenite nucleates predominantly at prior austenite grain boundaries and exhibits an austenite memory effect. A multi-phase field model has been coupled with a nucleation model to describe austenite formation from martensite. Martensite is considered as carbon-supersaturated ferrite with cementite and austenite formation assumed to occur under para-equilibrium conditions, i.e., controlled by carbon diffusion. The proposed model successfully reproduces the experimental austenite transformation kinetics up to a transformed fraction of about 0.9, while deviations appear in the final transformation stage, likely reflecting mechanisms not explicitly included in the present framework, such as the diffusion of substitutional alloying elements, i.e., Mn. This study provides significant insights into the rapid reverse transformation mechanism in fine-grained martensitic steels, which is crucial for predicting and controlling the properties of welded joints in ultra-high strength steels.