Grain size dependent texture evolution in severely rolled pure copper

• The texture in rolling of copper is grain size dependent in the UFG regime.
• The UFG brass-type texture is due to massive {111} < 112 > partial slip.
• The strain mode changes from tangent to Taylor for CG and UFG grain size respectively.
• The GND density decreases strongly when UFG grains are rolled.

Large strain rolling – up to 97% thickness reduction – was carried out on pure copper with two different initial grain sizes: coarse-grained (CG, 24 μm) and ultrafine-grained (UFG, 360 nm). After rolling, classical copper-type rolling texture was obtained for the CG copper while a brass-type rolling texture was observed in the starting UFG copper, obtained by eight-pass equal channel angular pressing at room temperature prior to rolling. Using the Viscoplastic Self Consistent polycrystal model, it is found that the deformation mechanism at large rolling strain is grain size dependent and a change in the major slip mode has a large impact on the type of deformation texture. The brass-type texture in the UFG material can be simulated using {111} < 112¯> partial slip together with {111} < 11¯0 > slip and a small amount of twinning; for the CG material, only {111} < 11¯0 > slip is needed to reproduce the copper-type rolling texture. Further, it is found that the polycrystal deformation condition approaches Taylor behavior in the UFG material whereas much more strain heterogeneity is present in rolling of the CG copper. By orientation imaging electron microscopy the geometrically necessary dislocation (GND) density is found to be decreasing in the UFG rolled samples while increasing in the CG case. This tendency corroborates the texture simulation parameters concerning strain heterogeneity.