TWIP steel

Twinning-Induced Plasticity steel which is also known as TWIP steel is a class of austenitic steels which can deform by both glide of individual dislocations and mechanical twinning on the {1 1 1}_γ<1 1 ${\displaystyle {\bar {2}}}$>_γ system.^[1] They have outstanding mechanical properties at room temperature combining high strength (ultimate tensile strength of up to 800 MPa) and ductility (elongation to failure up to 100%) based on a high work-hardening capacity. TWIP steels have mostly high content in Mn (above 20% in weight %) and small additions of elements such C (<1 wt.%), Si (<3 wt.%), or Al (<3 wt.%). The steels have low stacking fault energy (between 20 and 40 mJ/m²) at room temperature. Although the details of the mechanisms controlling strain-hardening in TWIP steels are still unclear, the high strain-hardening is commonly attributed to the reduction of the dislocation mean free path with the increasing fraction of deformation twins as these are considered to be strong obstacles to dislocation glide. Therefore, a quantitative study of deformation twinning in TWIP steels is critical to understand their strain-hardening mechanisms and mechanical properties. Deformation twinning can be considered as a nucleation and growth process. Twin growth is assumed to proceed by co-operative movement of Shockley partials on subsequent {111} planes.