Factors influencing the shearing patterns in equal-channel angular pressing

The shearing patterns are calculated for equal-channel angular pressing (ECAP) under three different conditions: (i) rotation of a sample around the X-axis when using a die angle of 90°, (ii) rotation around the X-axis when using a die angle of 120° and (iii) rotation around the Y- and Z-axes when using plate samples with a die angle of 90°. Separate sets of shearing patterns are constructed for the four standard processing routes: route A with no rotation of the sample between consecutive passes, routes BA and BC with rotations of 90° in alternate directions or the same direction between each pass, and route C with a rotation of 180° between passes. It is concluded that the development of a uniform microstructure of equiaxed grains, separated by high-angle grain boundaries, is favored using route BC because (i) shearing occurs over large angular ranges on the three orthogonal planes within the sample, (ii) there is a regular and periodic restoration of an equiaxed structure during consecutive pressings and (iii) deformation occurs on each orthogonal plane.