Circumferential twisting during route B equal-channel angular pressing

Equal-channel angular pressing (ECAP) is a representative severe plastic deformation process to fabricate bulk nanostructured materials by repetitive passes. Typically, there are four basic processing routes for the repetitive passes: route B is the most beneficial for grain refinement and homogenization of microstructure. In this work, investigation on deformation during route B in ECAP was conducted using the finite element analysis. It was found that the route B could lead to the inhomogeneous equivalent strain along the longitudinal direction of the workpiece by an unusual phenomenon called “circumferential twisting”. The circumferential twisting is primarily attributed to the deformation inhomogeneity for the cross-section induced during the 1 st pass of ECAP. This phenomenon occurs remarkably for the large-scale ECAP process because the twisting angle per unit length is almost constant. In addition, the higher the strain hardening exponent of the material, the greater the sample twisting during ECAP by the corner gap effect.