Transformation matrix analysis on the shear characteristics in multi-pass ECAP processing and predictive design of new ECAP routes

In this paper, transformation matrices are established to describe the orientation transformation of the planes and directions in a sample during multi-pass equal channel angular pressing (ECAP) processing. From this basis, the shearing characteristics associated with multi-pass ECAP processing in different processing routes are analyzed, and a new ECAP route expected to be more effective for grain refinement and particle redistribution is proposed. With the aid of transformation matrix analysis, it is demonstrated that route BC involves a redundant strain process and, hence, is not very effective for particle redistribution but is useful for grain refinement. The experimental results prove that the new proposed ECAP route, called route BC-UD2, is more successful for both grain refinement and particle redistribution. The established transformation matrix analysis method is helpful both in analysis of the shear characteristics of multi-pass ECAP processing and in the design of new ECAP routes.