Tensile-deformed high-manganese austenitic steels exhibiting twinning-induced plasticity were analyzed by means of electron back-scattering diffraction and X-ray diffraction in order to examine the influence of differences in stacking-fault energy on twinning activity during deformation. The steel specimen, with a stacking-fault energy of 15mJ/m2, had a microstructure with a higher population of mechanical twins than that of a steel specimen having a stacking-fault energy of 25mJ/m2. The <111> and <100> fibers developed along the tensile axis, and mechanical twinning occurred preferentially in the <111> fibre. The Schmid factors for slip and twinning deformations explained the origin of higher twinning activity in the <111> fibre. A high stacking-fault energy suppressed the twinning activity, even in the <111> fibre. A line profile analysis, based upon the X-ray diffraction data, revealed the relationship between the characteristics of the deformed microstructures and the stacking-fault energies of the specimens. Although the variation in dislocation density with tensile deformation was not affected by the stacking-fault energies, the effect of the stacking-fault energies on crystallite size-refinement became significant with decreasing stacking-fault energy. The stacking-fault probability, estimated from a peak-shift analysis of the 111 and 200 diffractions, was high for the specimen with a low stacking-fault energy. Regardless of the difference in the stacking-fault energies of the steel specimens, the refined crystallite size was correlated with the stacking-fault probability, indicating that whether the deformation-induced crystallite-size refinement occurred depended directly upon the stacking-fault probability rather than upon the stacking-fault energies in the present steel specimens.

Microstructural Characterization of High-Manganese Austenitic Steels with Different Stacking Fault Energies. S.Sato, E.P.Kwon, M.Imafuku, K.Wagatsuma, S.Suzuki: Materials Characterization, 2011, 62[8], 781-8