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Equal channel angular pressing provides a convenient procedure for introducing an ultrafine grained microstructure into materials. In this paper, the deformation distribution of cylindrical billet with different diameters during equal channel angular pressing (ECAP) was simulated using 3D finite element models. The plastic strains in three perpendicular planes of the billet are predicted. And the influence of the friction between billet and channel on the equivalent plastic strain is also determined. The results show that the equivalent plastic strains are inhomogeneous in three directions and the inhomogeneity of the strain distribution inside ECAPed materials is slightly related to their diameters, which means larger scale UFG materials can be achieved via ECAP process.

Uniaxial compressive experiments of ultrafine-grained (UFG) copper fabricated by equal channel angular pressing method were performed at temperatures ranging from 77 K to 573 K under quasi-static and dynamic loading conditions. Based on the experimental results, the influence of temperature on flow stress, strain hardening rate and strain rate sensitivity (SRS) were investigated carefully. The results show that the flow stress of UFG copper displays much larger sensitivity to testing temperature than that of coarse grained copper. Meanwhile, both the strain hardening rate and its sensitivity to temperature of UFG copper are lower than those of its coarse counterpart. The SRS of UFG copper also shows apparent dependence on temperature. Although the estimated activation volume of UFG-Cu is on the order of ~10 b³, which is on the same order with that of grain boundary diffusion processes, these processes should be ruled out as dominant mechanisms for UFG-Cu at our experimental temperature and strain rate range. Instead, it is suggested that the dislocation-grain boundary interactions process might be the dominant thermally activated mechanism for UFG-Cu.

Equal channel angular pressing provides a convenient procedure for introducing an ultrafine grained microstructure into materials. In this paper, the deformation distribution of cylindrical billet with different diameters during equal channel angular pressing (ECAP) was simulated using 3D finite element models. The plastic strains in three perpendicular planes of the billet are predicted. And the influence of the friction between billet and channel on the equivalent plastic strain is also determined. The results show that the equivalent plastic strains are inhomogeneous in three directions and the imhomogenuity of the strain distribution inside ECAPed materials is slightly related to their diameters, which means larger scale UFG materials can be achieved via ECAP process.

Samples of pure Cu cylinder were plastically deformed by combination of cold-forging (CF) and cold-drawing (CD) under the liquid nitrogen temperature (LNT). X-ray diffraction measurements indicate that an increase of deformation strain leads to a decrease in crystallite size and an increase in twin densities for the CF and CD processed ultrafine-grained (UFG) samples. Dynamic recovery is suggested to start during the deformation process, and leads to a decrease of dislocation density at large deformation strains. The increase of twin density could compensate the loss of microhardness because of the decreasing of dislocation density. The electrical conductivities of CF+CD samples were tested through standard four-probe method, all of which are higher than 92% IACS. The results suggest that the strength of pure Cu could be improved and still keep its relatively high electrical conductivity by introducing deformation twins (DTs) into its microstructure.