Evolution of crystallographic texture and material anisotropy effects resulting from uniaxial deformation for...

Steels used in the automotive industry have seen significant improvements within the past few decades, as economic and environmental efficiency play major and increasing roles in current individual transportation. In particular, it has been possible to combine high formability with high strength, which contributes to passenger safety, vehicle performance and efficiency. Deep-drawing steels with higher manganese content play a special role in the class of automotive body sheet materials, in which the final mechanical properties are achieved, for example, through twinning-induced plasticity and/or transformation-induced plasticity effects. In this study, the deformation behavior of steels X40MnCrAlV-19-2.5-2, HCT690T and S355MC was investigated using laboratory X-ray diffraction analyses. The investigations cover the evolution of crystallographic texture and material anisotropy resulting from uniaxial deformation, as well as their influence on diffraction data, especially in the context of stress analyses. In contrast to the situation in the initial as-rolled state, the induced deformations up to the limit of uniform elongation lead to the formation of strong textures and a considerable impairment of the diffraction data due to material anisotropy. However, the formed crystallographic textures do not suffice to describe this impairment. Rather, this effect is mainly attributable to intergranular strains, which are caused by different degrees of deformation of individual crystallites within the elasto-plastic regime. These phenomena need to be considered, and this is demonstrated using the application example of a welded metal sheet. Correction approaches are proposed and their application is illustrated, with a focus on how readily the residual stresses can be evaluated.