Influence of stacking fault energy and temperature on microstructures and mechanical properties of fcc pure metals processed by equal-channel angular pressing

摘要

Three fcc pure metals-Cu, Ni, and Al, with the same purity level (～9.99 wt%) and different stacking fault energies (SFEs, about 45 mJ/m~2,125 mJ/m~2, and 166 mJ/m~2, respectively) are processed by equal-channel angular pressing (ECAP) at different temperatures (room temperature, 0.32T_m, and 0.4T_m). A dislocation density-based model is improved by introducing a material-dependent parameter, and the improved model is utilized to predict the evolution of dislocation density, grain size, and strength of materials processed by ECAP processing. The predicted dislocation density, grain size, and strength are compared with the experimental results, with satisfactory agreement. The influence of the SFE on the steady-state grain size d_s is discussed, based on the experimental and modeling results. It is demonstrated that at the same homologous temperatures, the dependence of the d_s on the SFE exists, and that a reduction in the SFE leads to a decrease in the d_s, in case there is no recrystallization in the samples. In addition, increasing deformation temperature leads to a decrease in the dislocation densities and an increase in the steady-state grain size d_s. The predicted values of the d_s match well with the experimental results at lower homologous temperatures.