The reversal in the temperature dependence of the elastic limit accurately determines the Mσs temperature of retained austenite in 4340 steel. Two models, one based on an exponential distribution of pre-existing nucleation sites and another based on an autocatalytic-site potency distribution, were compared in predicting the constitutive behavior of the steel in the stress-assisted transformation regime (T < Mσs). The autocatalytic-site potency distribution is in better agreement with the experimental stress-strain behavior and predicts reasonable values of the carbon enrichment of the retained austenite due to tempering. The decrease in the chemical driving force for the transformation of retained austenite due to carbon stabilization determines the elastic limit of the steel in the stress-assisted transformation regime.
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