Modeling the Flow Response of Severely Processed Metals: Application to Copper and Zirconium

Irene J. Beyerlein Staff Scientist Theoretical Division Los Alamos National Laboratory Los Alamos, NM 87545 Irene@lanl.gov Severe plastic deformation techniques have received considerable attention for their potential in producing nanocrystalline metals with outstanding properties. As the name suggests, these techniques involve deforming metals up to extremely large strains, from 100% to 1600%. To measure their mechanical performance, subsequent uniaxial tests or hardness measurements are conducted on the heavily processed samples. In most situations, the severely processed material is plastically anisotropic, meaning that the yield stress and hardening evolution depend on the strain mode and direction imposed by the test. So for example the tensile strength of the material could be stronger along the billet axis than transverse to it. The opposite may occur in compression. Furthermore, subsequent loading most often imposes a strain-path change to the material. Both strain-path changes and large plastic straining have for some time challenged development of models for metal deformation. We are currently developing micromechanical hardening laws and multi-scale models for the deformation behavior of metals with a large strain processing history. The resulting constitutive model accounts for contributions to anisotropy by texture and microstructural evolution in pre-straining and re-loading. In this talk, the predictions will be compared with the measured responses in copper and zirconium after they have been processed by equal channel angular extrusion. The model forecasts significant asymmetry in the tension and compression responses and directional dependence of these metals after ECAE, in agreement with observation

Location: Seaver Science LIbrary (SSL) Rm 150

Audiences: Everyone Is Invited

Contact: April Mundy