Candidature of equal channel angular pressing for processing of tubular commercial purity-titanium

The equal channel angular pressing (ECAP) process is a promising technique for imparting a large plastic deformation to materials without a resultant decrease in cross sectional area. In the present study, the suitability of this technique for the processing of tubular specimens has been investigated. Commercially pure titanium was selected for the study. Tubular specimens were extruded to three passes using two processing routes through an ECAP die with an angle of 150 degrees between the two intersecting channels. Sand was used as a mandrel during the pressing. Analysis of force-stroke diagram was carried out, work from registered force-stroke diagram was calculated and compared with theoretical calculations. The mechanical properties and the microstructure were also investigated. To determine the influence of surface area to volume ratio of the specimens (referred to as the shape difficulty factor, SDF), data obtained in the current study on ECAP of tubular CP-Titanium was compared with data available in the literature on Hooker extrusion and conventional solid extrusion of CP-Titanium. Improvement in mechanical properties was observed in both the Routes. The grain size was reduced from similar to 18 mu m to similar to 12 mu m. These investigations demonstrate that ECAP is a promising technique for improving properties of tubular materials while ensuring retention of shape (with the possibility of imparting further deformation to the specimen using the same die) and with low pressing pressures. (c) 2005 Elsevier B.V. All rights reserved.