Ultra-fine grained bulk CP-Ti processed by multi-pass ECAP a warm deformation region

In order to refine the grain size of commercially pure titanium (CP-Ti) to a submicrometer scale, equal channel angular pressing (ECAP) was attempted at a temperature range of 200-300 degrees C. The experiments revealed that, 250 degrees C was the minimum temperature at which ten passes of ECAP could be performed in a 105 degrees die without the cracking of billets. An ultrafine-grained (UFG) microstructure with a mean grain size of 183 nm was achieved after 10 passes. The processed CP-Ti displayed high tensile strength of 892 MPa and high elongation to failure of 20.5%. The enhancement in mechanical properties is explained in terms of grain refinement and dislocation density increasing. The high ductility of UFG pure Ti with the absence of strain hardening behavior is attributed to its enhanced strain rate sensitivity. (C) 2013 Elsevier B.V. All rights reserved.