Deformation Geometry and Through-Thickness Strain Gradients in Asymmetric Rolling

Abstract

Experiments and simulations focusing on cold rolling under conditions where the work roll velocities are different (asymmetric rolling) have been performed to provide a basic framework for understanding the effects of the roll velocity ratio and deformation geometry on through thickness shear strain development. It is shown that deformation geometry, controlled by varying the reduction per pass, has a significant impact on the through thickness shear strain gradients at a given level of asymmetry. Large reductions per pass lead to more uniform through thickness shear strains, but lower overall shear strain magnitudes compared to rolling conditions involving small reductions per pass. Moreover, the results show that a critical value of the roll velocity ratio exists, for a fixed set of rolling conditions, above which the shear strains induced by asymmetric rolling remain unchanged. This is interpreted based on the relative importance of geometrically induced shear strains and those arising from frictional effects. In this context, the position of the neutral points plays a vital role.

Differential speed rolling of Ni3Al based intermetallic alloy—Analysis of the deformation process

“…It is evident that, the strain rises in parabolic course with increase of the R value. This situation should be explained in terms of a presence of additional shear strain, which value is proportional to the roll-speed mismatch [17]. A higher imposed strain by the DSR may be also attributed to an activation of additional slip system 〈1 1 0〉 {1 0 0} resulting from an increase of the strain rate [18], which linearly rises with the R value (Fig.…”

“…Plots of a calculated accumulated strain (a) and strain rate (b)[17] and measured microhardness change ((c)-after 2 rolling passes) as a function of the rolls velocity ratio R. (d) Tensile curves obtained for sample in the initial state and after 2 rolling passes with different values of the R (TYS-tensile yield strength, UTS-ultimate tensile strength).…”

Heterogeneous lamella structure unites ultrafine-grain strength with coarse-grain ductility

“…The HL structure was produced by asymmetric rolling (13,14) and subsequent partial recrystallization (see Materials and Methods for details). The asymmetric rolling elongated the initial equiaxed grains (Fig.…”

Asymmetric cryorolling for fabrication of nanostructural aluminum sheets

“…Therefore, the high angle grain boundaries in the samples for RUDV of 1.1 should result in its lower ductility compared with that for RUDV of 1.4. Roumina et al15 also found that the Al alloy strips exhibit high formability when they are produced via the shear deformation.…”