Microstructural evolution during uniaxial tension-compression in-plane deformation of an IF steel

In many metallic materials, load path changes result in Bauschinger effects, i.e., a reduction of yield strength. In this study, we present results of a microstructural investigation on Bauschinger effects in the sheet metal DC06 subjected to in-plane uniaxial loading. We performed tension-compression tests with different values of maximum tensile strains in a novel tool that was especially designed to prevent buckling under compressive loading subsequent to tension. The material exhibits a distinct Bauschinger effect when subjected to the corresponding load path change, which can be rationalized by considering the results of TEM and EBSD investigations on the evolution of dislocation substructures, and of X-ray diffraction measurements of residual stresses, at the different stages of uniaxial loading. Our experimental results clearly show that a combination of different dislocation densities in different grains and back stresses caused by pile-ups of geometrical necessary dislocations leads to the Bauschinger effect observed in the DC06 sheet material.