Papers by Author: R. Srinivasan

Abstract: Two-Dimensional finite element analysis was carried out to optimize the equal channel angular pressing process (ECAP) for strain homogeneity under frictionless and frictional conditions. The effect of outside corner angle (Ψ), inner radius (r) and shear friction (m) on the strain homogeneity was investigated. The strain homogeneity can be increased by correcting the outside corner to eliminate the corner gap between the sample and the die at the expense of average strain. Small inside radius and outside corner radius would provide large deformations without much loss in the strain homogeneity under frictionless conditions. The work piece deformation is by bending if the inner radius exceeds a critical value. No improvement in strain homogeneity was observed under frictional conditions.

Abstract: Over the past two decades equal channel angular processing (ECAP) and other severe plastic deformation (SPD) processes have been shown, in the laboratory scale, to produce material with promising properties for industrial applications. In particular, ultrafine grain (UFG) metals produced by ECAP process, for example, have been shown to exhibit higher strain rate sensitivity at lower temperatures and higher strain rates. These factors translate to improved hot formability. However, scale up of these processes to manufacture industrial size components has not been widely undertaken. In this study, billets of annealed AA6061 with 12.5 mm (0.5-in), 50 mm (2-in) and 100 mm (4-in) square cross section were ECAP processed. For the first time, these larger SPD billets were used as starting stock for subsequent hot forging. Several parts were forged on an industrial scale press with the UFG material, as well as conventional stock materials. These parts varied in complexity, as well as size in order to cover the variability in industrial components. This paper will present the effect of scaling up on the mechanical properties, microstructure, and the hot workability of the alloy from the laboratory scale (12.5 mm) to industrial scale (100 mm). Results show that both the forging temperature of the billets and the starting billet size can be substantially decreased compared to conventional forging practice. Therefore, the use of SPD materials, as forging stock, results in decreased energy usage and increased material yield. Results presented will include examples of forged parts, estimated energy savings associated with the use of SPDUFG stock, and properties after forging and subsequent heat treatment.