investigating the effect of process order and die shape on the mechanical properties of copper in combined severe plastic deformation of twist extrusion and ecap

Investigating production techniques and enhancing the mechanical properties of fine-grained materials has been a focus of extensive research in recent years. the production of fine-grained materials free from impurities and porosity through severe plastic deformation methods has made these techniques increasingly appealing. in this research, the combined extrusion process was carried out using a die that included two twisting and ecap channels in two modes: direct and reverse. the forming force, strain, and hardness generated in the specimen were determined using finite element analysis, 2d/3d deform software, and the vickers micro-hardness test. it was found that the maximum value of the forming force in the reverse process has increased by 30%, while the standard deviation of the strain and hardness values measured in the cross-section of the specimen decreased by 73% and 56%, respectively. this created much more uniform strains in one process passes, which is one of the main goals of the severe plastic deformation method. evaluating the effect of design variable sizes showed that the average forming force and the maximum strain increased by 48% and 44%, respectively, as the ratio of the large diameter to the small diameter, m, of the elliptical region in the twisting channel of the die increased. additionally, as the twist angle θ increased, these parameters rose by 35% and 63%, respectively, while an increase in the internal angle of ecap, α, led to a 33% reduction in the average forming force and a 22% decrease in the maximum strain generated.