Investigation of sample size effect on the deformation heterogeneity and texture development during equal channel angular pressing

Abstract

Equal channel angular pressing (ECAP), or equal channel angular extrusion (ECAE), is a very promising severe plastic deformation technique for producing ultra-fine grained (UFG) materials. Up to now, many works have been contributed to understand the influence of die geometry, frictional condition and back-pressure during the ECAP process. Most of them only focused on a specific sample size, and very few investigations about the sample size effect have been reported. Therefore, the present investigation was designed specifically to provide systematical information on the influence of sample size on the deformation heterogeneity and texture development after ECAP. To the authors’ knowledge, this is the first attempt to consider the sample dimension influence on the texture evolution of ECAP processed aluminum single crystals. Study has been successfully conducted using crystal plasticity finite element model for four different samples having widths between 2mm and 40mm. For each of sample, the simulated effective plastic strain is close to the theoretical value. The calculated shear strength and stress decreased slightly with the sample width, but show very little change at larger samples. Simulation results revealed similar deformation heterogeneity during the process as the reference. The predicted {111} pole figures and activity of slip systems indicate that the texture evolution is independent of the sample dimension. Simulation results are consistent with the experimental observations when the same initial crystallographic orientation and sample size have been used. The present work offers a good suggestion for the scaling up of the ECAP process for the industrial application from the views of both deformation pattern and evolution of texture.