Professor, School of Mechanical Engineering/Director, Department of Mechanical Engineering and Automation, University of science & Technology of Beijing, China.

Speech Title: Crystal plasticity based modeling of slip-twinning associated strain hardening for copper single crystal in large plastic deformation
Abstract: Microstructure based variational strain hardening behaviour of single crystal and polycrystal significantly depends on the competition and collaboration between dislocations slip and deformation twinning. For copper single crystal particularly in large plastic deformation, to clarify and represent the corresponding deformation mechanisms for the segmented strain hardening regions, a crystal plasticity based modeling of strain hardening characteristics associated with slip and twinning interactions is proposed. At the initial hardening stage, accumulated twin volume fraction is incorporated into the evolution of slip resistance to model the slip-twinning (S-T) interactions. Then the followed hardening decreasing stage caused by the twinning reorientation is related with the twinning-twinning (T-T) interactions. When deformed to large strains, a hardening law including slip-slip (S-S) interactions in twinned region and accumulated slip is presented. The influence of initial crystal orientation, twinning reorientation and S-S interactions on hardening stages are studied respectively. It is concluded that the dominating hardening mechanism at the initial hardening stage has been identified via investigating the slip and twinning activities. The hardening model reproduces stress decreasing observed in the experiments. In addition, the S-S interactions in twinned area could be captured and lead to an obvious stress increasing at large strains.
Keywords: Copper single crystal; Strain hardening; Twinning; Large plastic deformation; Crystal plasticity.