Warm deformation behaviour of UFG CP-Titanium produced by I-ECAP

The objective of the present study is to investigate the deformation behaviour of Ultrafine-grain (UFG) commercial purity Titanium (CP-Ti) at warm temperatures. Firstly, CP-Ti billets were processed through six passes of incremental equal channel angular pressing (IECAP) at 300 degrees C using a die channel angle (Phi) of 120 degrees. Uniaxial compression tests were then performed under isothermal conditions on cylindrical samples obtained from the UFG CP-Ti billets. A series of these tests were conducted at different temperatures of 400, 500 and 600 degrees C and at varying strain rates of 0.01, 0.1 and 1.0 s(-1). In each test, the original height of the sample was deformed by similar to 50% of its original value. The true stress-strain curves obtained, revealed that the flow stress was sensitive to both temperature and strain rate. In general, the flow stress was higher for lower temperatures and higher strain rates. For tests conducted at 400 and 500 degrees C, the flow stress quickly reaches a peak value, beyond which it exhibits a steady state response where there is no appreciable change in flow stress with increasing strain. The 600 degrees C tests however shows a strain hardening behaviour. Microstructure of the sample deformed at 600 degrees C and 0.01 s(-1), exhibited significant grain growth.