Microstructure and properties of pure Ti processed by ECAP and cold extrusion

Equal channel angular pressing (ECAP) has been used to refine the grain siz e of commercially pure (CP) Ti as well as other metals and alloys. CP-Ti is usually processed at about 400 degreesC because it lacks sufficient ductil ity at lower temperatures. The warm processing temperature limits the capab ility of the ECAP technique in improving the strength of CP-TI. We have emp loyed cold extrusion following warm ECAP to further refine the grains and i mprove the strength of CP-Ti. Ti billets were first processed for eight pas ses via ECAP route B-C, with a clockwise rotation of 90 degrees between adj acent passes. They were further processed by successive cold extrusions to an accumulative reduction in cross-section area by 47 or 75%. This paper re ports the surface quality, microstructures, microhardness, tensile properti es, and thermal stability of these Ti billets processed by a combination of ECAP and cold extrusion. (C) 2001 Elsevier Science B.V. All rights reserve d.