TEM investigation of the formation mechanism of deformation twins in Fe–Mn–Si–Al TWIP steels

Abstract

The microstructure of a Fe–Mn–Si–Al twinning-induced plasticity (TWIP) steel exhibiting remarkable work hardening rate under uniaxial tensile deformation was investigated using transmission electron microscopy to uncover the mechanism(s) controlling the nucleation and growth of the mechanically induced twins. The results show that the stair-rod cross-slip deviation mechanism is necessary for the formation of the twins, while large extrinsic stacking faults homogenously distributed within the grains could act as preferential sources for the activation of the deviation process. The influence of such features on the thickness and strength of the twins and the resulting mechanical behaviour is discussed and compared to similar works recently performed on Fe–Mn–C TWIP steels.

Keywords:

• Fe–Mn–Si–Al TWIP steels
• transmission electron microscopy
• extended defects
• twinning mechanisms

Acknowledgements

This work was carried out in the framework of the IAP program of the Belgian State Federal Office for Scientific, Technical and Cultural Affairs, under [Contract No. P7/21]. P.J. Jacques acknowledges the FRS-FNRS.