Internal elastic strains in an IF steel following changes in strain path

Abstract

Residual elastic strains present in an IF steel following rolling and subsequent tensile deformation have been evaluated using X-ray diffraction. It was possible to decompose diffraction profiles into two symmetrical components notionally corresponding to dislocation walls and cell interiors and so estimate the volume fractions and mean elastic strains associated with these components of the microstructure following different deformation modes. The residual long range elastic strains were very small following rolling, but they were much greater following subsequent tensile elongation to macroscopic yield. The mean strains could only account for about one-third of the strain induced anisotropy of flow stress. It is concluded that insufficient dislocations accumulate at cell walls at macroscopic yield following a path change to give homogeneous loading of the dislocation walls, and that this effect can account for the difference between the macroscopic mechanical behaviour and predictions from the X-ray strain measurements.