TENSILE PROPERTIES AND DISLOCATION STRENGTHENING OF CP-TI PROCESSED BY EQUAL-CHANNEL ANGULAR PRESSING AT 723K

摘要

In present study, equal channel angular pressing (ECAP) of a quenched commercially pure titanium (CP-Ti) (grade 2) has been successfully performed at 723 K with an imposed equivalent normal strain of about ～0.5, and its tensile properties and dislocation strengthening was investigated. A high yield strength of ~680 Mpa (36 % higher than that of the unECAPed CP-Ti) in terms of CP-Ti has been observed. In addition to the strengthening, this processing allows the ECAPed CP-Ti have a high level of tensile ductility (~30 %). The dislocation strengthening contribution was estimated by using Taylor equation, where the dislocation density was calculated in terms of the value of the coherent diffraction domain size and the lattice micro-strain, which were obtained from XRD line broadening analysis. This theoretical analysis illustrates that ECAP-resulted dislocation make a strengthening contribution of about ~34.9 % for the improvement in strength.