Using single crystals of Hadfield steel (Fe-13Mn-1.3C or Fe-13Mn-2.7Al-1.3wt%C), a systematic investigation was made of slip, twinning, stages of plastic flow, and strain-hardening coefficient as a function of the orientation of the tensile axis. This was done using optical and electron microscopy and X-ray analysis. It was shown that the combination of low stacking-fault energy (30mJ/m2) and a high concentration of carbon atoms in aluminium-free steel resulted in the development of mechanical twinning at room temperature for all crystalline orientations. A new type of twinning, with the formation of extrinsic stacking faults, was found in [001] single crystals. It was established experimentally that alloying with aluminium led to an increase in the stacking-fault energy of Hadfield steel and suppressed twinning for all crystal orientations while preserving high values of the strain-hardening coefficient.

The Effect of Aluminium on Mechanical Properties and Deformation Mechanisms of Hadfield Steel Single Crystals. E.G.Zakharova, I.V.Kireeva, Y.I.Chumlyakov, A.A.Shulmina, H.Sehitoglu, I.Karaman: Journal de Physique IV, 2004, 115, 243-50