Grain boundary engineering in roll-bonded copper to overcome the strength-ductility dilemma

Abstract

Copper sheets with graded and fine-grained (FG) microstructures were processed by accumulative roll bonding (ARB) and subsequent annealing to evaluate the effect of structural heterogeneities on the strength–ductility relationship. By an appropriate design of the individual ARB-process-steps, two types of graded structures (GSs) have been achieved where the grain size gradually changes from a more refined grain structure at the surface to a coarser one in the interior (CGC) or a coarser one at the surface to a finer one in the interior (FGC). For both types, the grains size gradually changes between 4 and 19 microns across the thickness of samples. In terms of the uniform tensile work, GSs exhibited a superior combination of strength and elongation owing to the hetero-deformation induced strengthening. In addition to a good strain delocalization capability compared to their coarse-grained (CG) counterpart, the graded microstructures affect the crack paths in the non-uniform deformation regime.

Keywords

• Pure copper
• Heterostructured materials
• Gradient microstructures
• Strain delocalization