The effect of tooling design and properties of materials on fracture and deformation through equal channel angular pressing technique

Abstract

The submicrometer range of grain sizes was reached for AA5083 by using equal channel angular pressing at room temperature. While the submicrometer grains of AA5083 were stable up to annealing temperatures of 300 °C, the stability of these grains was only moderately maintained up to annealing temperatures of about 200 °C. Tensile tests conducted after one pass of equal channel angular pressing—that is, strain introduction of roughly one—showed a significant increase in the 0.2% proof stress and ultimate tensile stress values for each alloy. Concurrent with this improvement, the elongations to failure decreased. The analysis shows that the square root of the magnesium content in each alloy corresponds with the magnitudes of these stresses. In samples that were cold rolled, comparable values of proof stresses and ultimate tensile stress were obtained at equivalent strains. However, because of the induction of a very small grain size, elongations to failure were higher after applying equal channel angular pressing to similar strains greater than one. The effects of material constitutive behaviour, tool design, and friction conditions on metal flow, stress fields, and the tendency for tensile fracture during the equal channel angular pressing process were studied using a finite element modelling technique. A degree of non-uniform flow was noted that extended past the head and tail of the extrusion when materials were subjected to equal channel angular pressing with varying constitutive behaviours or when utilising tooling with a radiused front leg. It is anticipated that tool design and material qualities will have a considerable effect on tensile stresses and, in turn, the development of tensile damage during equal channel angular pressing.