Abstract
Most of the investigations on plastic deformation of metal single crystals have only considered the resolved shear stress component of the operating slip system and have ignored the existence of the normal stress component.
The present studies reported the deformation behavior of iron single crystals with a shear test in which the applied stress coincides with the slip system for crystal as a means to minimize the effect of the normal component.
The results obtained are summarized as follows:
(1) The resolved shear stress-shear strain curves for the tensile tests are parabolic for all orientations tested. However, in the shear tests, the shear stress-shear strain curves markedly differ from those in the tensile tests. In particular, at 195°K, when the shearing plane coincides with the (112) plane the three-stage hardening process is clearly observed in the stress-strain curve.
(2) Temperature dependence of the critical shear stress in shear deformation was markedly less than in tensile deformation. This suggests that the normal stress component is an important factor for controlling the mechanism of deformation. Moreover, in the shear deformation for the {112}⟨111⟩ and {110}⟨111⟩ slip systems, the variation of the critical shear stress with temperature was remarkably different. This means that Schmid’s law does not hold for bcc metal crystals, particularly at low temperatures.
