Understanding the relationship between mechanical twinning and dynamic strain aging (DSA) in austenitic steels is necessary for steel development. DSA can be manipulated by changing the strain rate during tension tests, or by alloying austenitic steels with aluminum. In the current study, 12.5%Mn-1.1%C austenitic steel and 24%Mn-0.45%C–2%Al austenitic steel were investigated under different strain rates. Increases in the strain rate resulted in an enhanced resistance of the steels to the plastic deformation only during early stages of strain (at 3% strain) because of mechanical twinning promotion. On one hand, at 25% strain under low strain rate deformation, the Al-alloyed steel showed a tendency to form more twin plates than the Al-free steel as indicated by the transmission electron microscopy. On the other hand, at 25% strain under a high strain rate deformation, the Al-free steel showed an enhanced twin plates propagation due to a stronger self-segregation/depletion of the interstitial atoms (the carbon concentration ranged between 0 and 11 at.%) as revealed by the 3D atom probe tomography. Furthermore, the Al-alloyed steel showed a reduced twin volume fraction with a strain rate increase due to shifting of the stacking fault energy to higher values. |
