The stress-strain behavior of single crystals of 12.34Mn-1.03wt%C Hadfield steel was studied, for the [¯111], [001] and [¯123] orientations, in tension and compression. The overall stress-strain response was strongly dependent upon the crystallographic orientation and the applied stress direction. Transmission electron microscopy and in situ optical microscopy demonstrated that twinning was the predominant deformation mechanism, at the onset of inelastic deformation, in [¯111] crystals which were subjected to tension and in [001] crystals which were subjected to compression. In the case of orientations which experienced twinning, the activation of multiple twinning systems produced a higher strain-hardening coefficient than that observed in typical face-centered cubic alloys. A model was presented which predicted orientation and stress-direction effects upon the critical stress for the initiation of twinning. The model took account of the role of local pile-up stresses, stacking-fault energy, influence of applied stress on the separation of partial dislocations, and an increase in the friction stress due to high solute concentrations. However, multiple slip was found to be the predominant deformation mechanism in [¯111] crystals which were subjected to compression and in [001] crystals which were deformed in tension. The [¯123] crystals underwent single slip in both tension and compression, with planar-type dislocations. By using electron back-scattering diffraction, macroscopic shear bands were identified which had a misorientation of 9º, in compressed [111] single crystals, at strains as low as 1%.

Deformation of Single Crystal Hadfield Steel by Twinning and Slip. I.Karaman, H.Sehitoglu, K.Gall, Y.I.Chumlyakov, H.J.Maier: Acta Materialia, 2000, 48[6], 1345-59