Comparison of twinning evolution with work hardening ability in twinning-induced plasticity steel under different strain rates

For Fe–22Mn–0.6C (wt%) twinning-induced plasticity (TWIP) steel with grain sizes of 35 and 170 μm, both the ultimate tensile strength and uniform elongation decrease with increasing the tensile strain rates (from 10 −4 to 10 0 s −1 ). The density of twin boundary (DTB) is presumed to be the major factor influencing mechanical properties. Accordingly, a parameter 2/( t + s ) ( t and s represent the thickness and spacing of deformation twins), also the inverse of the mean free path for dislocation slip, is proposed to characterize the planar-oriented twinned structure in infinite grain size ( D » t ≈ s ). It also evaluates the effect of DTB on the work hardening ability and ductility of the TWIP steel.