Grain size dependence of tensile strength of polycrystalline metals by crystal-plasticity-damage multi-scale analyses

This work investigates the grain size dependence of the macroscopic tensile strength of polycrystalline metals by applying the two-scale finite element method, which is based on the homogenization theory combined with the elastic-plastic-damage constitutive model for single crystal grain. The degradation of the macroscopic stiffness is realized by the damage evolution in micro scale in our two-scale finite element analysis. It is demonstrated that the tensile strengths of polycrystalline metals exhibit the Hall-Petch type dependence on the grain size and that the less ductile the corresponding material behavior the smaller the grain size. Then this work also tries to clarify the microscopic mechanisms of these grain size dependences.