The influence of temperature on stacking fault energy in Fe-based alloys

Temperature has great influence on the stacking fault energy (SFE). Both SFE and dγ 0/dT for Fe-based alloys containing substitutional or interstitial atoms increase with increasing temperature. Based on the thermodynamic model of SFE, the equation $\frac{{d\gamma _0 }}{{dT}} = \frac{{d\gamma ^{ch} }}{{dT}} + \frac{{d\gamma ^{se\user1{g}} }}{{dT}} + \frac{{d\gamma ^{MG} }}{{dT}}$ and those expressions for three items involved are established. The calculatedγ 0/dT is generally consistent with the experimental. The influence of chemical free energy on the temperature dependence of SFE is almost constant, and is obviously stronger than that of magnetic and segregation contributions. The magnetic transition and the segregation of alloying elements at stacking faults cause a decrease in SFE of the alloys when temperature increases; that is, dγ MG/dT<0 and dγ seg/dT<0. Meanwhile, such an influence decreases with increasing temperature, except for the dγ seg/dT} of Fe?Mn?Si alloys. With these results, the experimental phenomena that the SFE of Fe-based alloys is not zero at the thermo-dynamically equilibrated temperature (T 0) of the λ and ε phases and they are positive both atT>T 0 andT<T 0 can be reasonably explained.