On the selection of outlet channel length and billet length in equal channel angular extrusion

The deformation behavior during equal channel angular extrusion (ECAE) of a typical strain hardening material with different combinations of outlet channel length and billet length is simulated using the finite element method (FEM). The results are evaluated in terms of the strain heterogeneity along the longitudinal direction, the shape of the deformed billet, and the working load. It is shown that a shorter outlet channel leads to a longer steady-state region and a lower working load, but a higher tendency of upward bending of the deformed billet. The portion of the steady-state region in the billet increases with the billet length-to-width ratio until the ratio reaches a critical value. These effects are essentially attributed to the variation of friction forces operative in the outlet and inlet channels. For a given die design, less friction conduces to a longer steady-state region but a higher tendency of upward bending of the billet.