Indian Journal of Engineering & Materials Sciences Vol. 22, October 2015, pp. 527-533 Combining circular-to-rectangular direct extrusion and equal channel angular pressing: Analysis and simulation R Comaneci, L Zaharia & D Nedelcu* Technical University “Gheorghe Asachi” Iasi, D. Mangeron 61A, 700050, Iasi, Romania Received 6 March 2015; accepted 21 August 2015 An experimental and numerical study of equal channel angular pressing (ECAP) - as the most effective severe plastic deformation (SPD) process and circular-to-rectangular direct extrusion (CRDE) - as traditional deformation process - has been conducted as separate and combined processes, respectively. An analysis of the deformation mechanisms based on grain fragmentation due to the velocity discontinuities and corresponding shearing along them has been undertaken. To reveal the main aspects of the deformation processes in a comparative manner, a finite element analysis (FEA) is performed and the results are depicted in terms of strain distribution and working-load. Experimental tests have confirmed the FEA. To evaluate the improvement of the mechanical properties as effect of applying the two processing methods as separate and combined procedures, tensile tests are performed. An increase of the yield and tensile strength without a further reduction in ductility is found. The results of this study highlight the potential of combining CRDE and ECAP as an efficient processing route for production of high-performance materials. Keywords: Aluminum, Severe plastic deformation, Equal channel angular pressing, Finite element analysis, Extrusion Known as the most effective severe plastic deformation (SPD) process, equal channel angular pressing (ECAP) is a well-established method for achieving ultra-fine grained (UFG) materials, which have been subjected to intensive investigation due to the spectacular improvement of their mechanical properties 1,2 . UFG materials offer significant advantages in terms of large strength 3,4 , hardness 5 and ductility 6 , high strain rate and/or low temperature superplasticity 7,8 . As Hall-Petch relation shows, the strength of the metallic materials increases with decreasing of the grain size. Because the grain refinement is strongly related to the level of the strain received by the material during the plastic deformation, a number of processes involving plastic deformation are used for the refinement of the grains, such as thermomechanical treatments (TMTs), traditional plastic deformation, and SPD. Advanced TMTs not exceed 1 μm in terms of grain size 9 . In traditional deformation processes, such as direct extrusion, increasing in strain involves decreasing in cross-section area, so the maximum strain is given by the final dimensions of the work- piece. To increase the effective strain level, the cross-section of the work-piece has to remain unchanged in shape and dimensions so that the process can be resumed until the necessary accumulated strain is achieved. That happens when applying ECAP. To get optimal performance, ECAP is sometimes associated with heat treatments such as inter-pass annealing to achieve better ductility 10 or aging treatment to increase the strength 11 . Different methods have been applied to increase the strain. Among them, combining ECAP with other deforming processes such as subsequent cold rolling 12 , hydrostatic extrusion 13 leads to a higher strain in comparison with the separately applied processes. But only the level of the strain does not assure the grain refinement. In many traditional deformation processes, the grains become only elongated without an obvious refinement of the structure. For the fragmentation takes place, the elongated grains have to be crossed by shearing stresses that exceeding the strength in pure shear of the grains can start the fragmentation. Since the deformation process became a possible method for grain refinement and the microstructure and mechanical properties of the plastic-deformed materials are directly related to strain, understanding the mechanisms of the grain refinement and its effects on the mechanical —————— *Corresponding author (E-mail: dnedelcu@tcm.tuiasi.ro)