Researches On Deformation Behavior In Equal Channel Angular Pressing Of Copper, Aluminum And Cu-Ag Alloy

ECAP(equal channel angular pressing)is one of severe plastic deformation technology, which can effectively process bulk ultra-fine grains materials. Therefore, ECAP has become a hot spot of research at home and abroad. Cu-Ag alloy gets widely attention of its good strength and excellent conductivity. The traditional methods for deforming Cu-Ag alloy such as cold rolling and cold drawing often leads the size of the original material to be reduced, but ECAP can just compensate for this. In this article Cu-Ag alloy was pressed by ECAP, the microstructure and mechanical properties of the alloy were analyzed. The condition of material after deformation can be simulated with computer numerical simulation technology from some aspects as stress and strain distribution, and it can also analysis the influence of the stress conditions of materials and the technological factors during ECAP for the uniformity of materials. All of these conclusions will provide the theoretical foundation for the subsequent ECAP research. In this article, pure copper and aluminum which have same crystal structure with Cu-Ag alloy were selected as the research objects during the processing of simulation for the convenience of setting parameters of the material. The influence of ECAP process factors(extrusion path and mold inside Angle) and friction, back pressure on the deformation uniformity of material were analyzed.During the experiment, Cu-Ag alloy was pressed by ECAP with route A of 1~4 passes at the room temperature. The microstructure of the sample characteristics and its evolution and mechanical properties were researched by the optical microscope, scanning electron microscope, mechanical tensile test and hardness test. The results show that: the microstructure in longitudinal section and cross section of alloy were refined and the microstructure of Cu-Ag eutectic turned from granular into fibrous. The slip plane of materials were changed from(220) to(111) after ECAP and the strength of other slip plane is in a state of changing. The organization orientation of alloy is always changing. The mechanical properties of Cu-Ag alloy changed a lot after 4 passes of ECAP. The hardness increased to 64.92 HV of raw sample from 191.4 HV. The tensile strength of materials increased to 533.07 MPa from 323.42 MPa after 4 passes of ECAP. The elongation of material has reduced to 12.6% from 19.4%, but it dropped most after 1 pass then turned moderately. Multiple passes of ECAP can alleviate the strain hardening of material during the plastic deformation.In this paper, the processing of ECAP on pure copper and pure aluminum were simulated with finite element software DEFORM-3D at different deformation conditions(route A, Ba, Bc and inside corner angular 75 °, 90 °, 115 °). The results showed that the load of material during the whole deformation was not affected by ECAP route, but would getting increase with the inside corner angle been small. Material showed the best deformation uniformity under Bc among three kind of routes. The equivalent strain gradient decreases decreased and the whole deformation uniformity of materials increased with the increasing of deformation passes.Different friction factor(0, 0.05, 0.1) and the back pressure value(0, 30 mpa, 50 mpa) were setted up during the deformation in this paper. Under this condition, the ECAP deformation processing of pure copper was simulated. It draws the following conclusions: the deformation of material was more fully as the increasing friction and the degree of grain refinement increased as well. But the change of the equivalent strain distribution appears different in each part of sample and results in a decline of the deformation uniformity of the material as a whole. Put back pressure can effectively improve the strain rate of materials which can improve homogeneity of material deformation.