Strain hardening in single crystals of Hadfield steel

Orientation dependence of the mechanism of deformation, i.e., slip and twin ning, was studied at 300 K on single crystals of Hadfield steel. It was sho wn that mechanical twinning in [(1) over bar 11], [(1) over bar 44], and [0 11] crystals is developed upon tension from the very early deformation stag es. The high values of Theta in [(1) over bar 11] crystals are related to t he development of twinning on several twinning systems; in the [ (1) over b ar 44] and [011] crystals, the early stages of deformation are connected wi th twinning in a single system a/6[(2) over bar 11](111), and the passage t o the operation of several twinning systems is accompanied by an increase i n Theta. In [012], [(1) over bar 23], and [(1) over bar 13] orientations, t he early stages of deformation are determined by slip; later, a change of t he mechanism of deformation from slip to twinning occurs. For the first tim e, we revealed mechanical twinning upon tension of [001] crystals and showe d that there is an orientational dependence of resolved shear stresses rela ted to the orientational dependence of the mechanisms of deformation by sli p and twinning. Dislocation mechanisms of twin nucleation in Hadfield steel are suggested.