Microstructure and mechanical properties of a commercially pure Ti processed by warm equal channel angular pressing

Abstract

A commercially pure (CP) Titanium alloy classified as Grade 1, was processed by Equal Channel Angular Pressing (ECAP) up to 4 passes in the temperature range of 450-150 degrees C.; The resulting microstructures were observed by Electron Back-Scattered Diffraction, revealing a bimodal grain size distribution consisting of small recrystallized grains of submicrometer size, with an average value of 0.3 mu m, and elongated bands of 1.4 mu m with different degree of substructure. Additionally the fraction of restored and deformed grains were evaluated as a function of processing temperature following an internal grain misorientation criterion, leading to an overall fraction of recrystallized grains between 40% and 20% in samples ECAPed at 450 and 150 degrees C, respectively.; The strengthening contributions of the grain size, equivalent oxygen content (O-eq) and Low Angle Grain Boundaries (LAGBs) to the yield stress were identified by the Hall Fetch and Taylor equations. The strengthening coefficient k of the Hall-Fetch relation was approximately 5 MPa mm(-1/2), with an increment of 0.44 MPa mm(-1/2) per 0.1 O-eq.-%, while the LAGB strengthening contribution was responsible approximately by half of the experimental yield stress values measured. (C) 2014 Elsevier B.V. All rights reserved.