High-manganese austenitic TWIP steels exhibit very high strength and elongation before necking. The
peculiarity of these steels is that mechanical twins form during straining due to their low stacking fault
energy (SFE). These twins are usually thought to have a huge impact on the outstanding properties of
the materials, either by bringing about a dynamic Hall & Petch effect and/or a composite effect. In this
study, the appearance of mechanical twins during tensile straining is investigated for a Fe–20%Mn–1.2%C
TWIP steel. The twinning rate was estimated by means of point counting analysis on EBSD micrographs
at different strain levels. The reliability of this method is first thoroughly discussed. It is then shown that
there exists a first order relationship between this twinning rate and the work hardening rate.