Effect of Si content on the stacking fault energy in γ-Fe–Mn–Si–C alloys: Part II. Thermodynamic estimation

Abstract

Thermodynamic estimation of the stacking fault energy (SFE) was performed in γ-Fe–31Mn–(0.25–8.67) Si–0.77C (at%) alloys, and the contribution of the antiferromagnetic transition to SFE is discussed. The results show that the non-magnetic component of SFE increases with increasing Si content, the magnetic component, i.e. the magnetic free energy caused by the antiferromagnetic order, depends on the average atomic moment and Néel temperature and increases SFE in the antiferromagnetic state. In addition to generating the chemical free energy change, Si in γ-Fe–Mn–Si alloys affects SFE through influencing the antiferromagnetic behavior including an increase in the localized magnetic moment on the Fe atom sites, a decrease in the Néel temperature and an anomaly in shear modulus. The anomaly in shear modulus due to the antiferromagnetic order is the important factor affecting SFE and must be considered in the investigation of SFE in the magnetic materials.