Dislocation microstructures in steel during deep drawing

Abstract

Simple and complex loadings are performed on low-carbon steel sheets in order to simulate deep drawing. The loading include uniaxial tension, plane strain, equibiaxial stretching, uniaxial tension followed by equibiaxial stretching, and reverse sequence. As the strain is increased dislocations tend to arrange themselves in walls delimiting cells of material in which the dislocation density is low. The cell shape and its evolution depend on the strain and the strain path. Some geometrical parameters (cell size, wall thickness) and wall orientation measurements allow the microstructure to be characterized. In each grain, dislocation walls appear to be connected with active slip planes. Cell size and wall thickness decrease with increasing strain along any strain path. During complex loadings the dislocation microstructure that develops is typical of the last loading path rather than the previous one.