Equal channel angular extrusion of tubular aluminum alloy specimens - Analysis of extrusion pressures and mechanical properties

The Equal Channel Angular Extrusion (ECAE) process is a promising technique for imparting large plastic deformation to materials without a resultant decrease in cross-sectional area. The die consists of two channels of equal cross section intersecting at an angle; the workpiece is placed in one channel and extruded into the other using a punch. In the present study, the suitability of this technique for processing of tubular specimen geometries has been investigated. Tubular specimens of an aluminum alloy were extruded to three passes through two processing routes using sand as a mandrel. The pressures required for extrusion were measured, and the mechanical properties of the extruded material were evaluated. The low extrusion pressures during ECAE of tubular specimens are due to the movement of the mandrel (sand) along with the specimen (drag friction acts in the same direction as the main punch force). On processing to three passes of ECAE (by inducing a strain of 0.9), the tensile strength, yield strength, and hardness are improved, and elongation to failure (percent) decreased as expected. The process requires low forming loads while ensuring retention of specimen shape. It is also possible to impart further deformation to the specimen using the same die. It is concluded that ECAE is a promising technique for improving properties of tubular specimens.