The Effect of Deformation Temperature on the Mechanical Properties and Microstructural Evolutions of High Manganese TWIP Steel

In this study, the effect of tensile test temperature (148 to 673 K) on the microstructural evolutions and the mechanical properties of high manganese twinning induced plasticity (TWIP) steel with the chemical composition of Fe- 31Mn-3Al-3Si (wt. %) was investigated. XRD, SEM and TEM were used to study the microstructural evolutions. Stacking fault energy (SFE) of the alloy was also calculated by a thermodynamic model. The results indicated that yield strength and tensile strength of steel were gradually decreased with increasing the temperature. However, total elongation reached a maximum value with increasing the temperature up to 248 K. Furthermore, microstructural investigations showed that in the temperature range of 473 to 673 K (SFE: 60-85mJ/m2), deformation was mainly controlled by dislocation gild and there was no evidence suggesting that twins were formed during deformation. In the temperature range of 248 to 473 K (SFE: 35-60mJ/m2), both mechanisms contributed to reacing a maximum ductility. In the temperature range of 248 to 148 K (SFE: 20-35mJ/m2), twinning and dislocation glide were still the dominant deformation mechanisms, but the change in the formation kinetic of twins probably led to decrease in the total elongation.