The influence of orientation and aluminium content on the deformation mechanisms of Hadfield steel single crystals

The low stacking fault energy and high carbon content in Hadfield steel make twinning the basic deformation mechanism from the onset of plastic deformation in [111] and [011] oriented single crystals in tension at T = 77-300 K. Alloying with aluminium (2.7 Al in wt.%) results in an increase of stacking fault energy from 0.03 J m2 to 0.05 J m^-2 and moves twinning to higher degrees of deformation (ϵpl > 15%). In aluminium-free [1-23] crystals twinning starts after 20% strain. For [123], [001] orientations, aluminiumadditions change the dislocation arrangement from a uniform distribution to a planar dislocation arrangment and also suppress twinning. Intersections of dislocation pile-ups were found to be the governing factor for hardening in the aluminium-Alloyed [001] crystals.