| The paper describes the peculiarities of Ti Grade 4 structure evolution depending on a number of ECAP-Conform passes. Billets with a diameter of 12 mm were subjected to ECAPConform processing with a number of passes from 1 to 10 at a temperature of 200 °C. It has been shown that accumulation of strain that happens, when the number of passes increases from 1 to 6 (e∼4.2), provides formation of an ultrafine-grained (UFG) structure with an average size of 250 nm in titanium. This leads to strength enhancement from 700 to 1020 MPa with some decrease of ductility. It has been established that further increase of the strain degree to ∼7.0 (10 passes) will result in additional enhancement of relative and uniform elongation with retention of the strength level. This happens due to increase of a fraction of high-angle boundaries in the UFG structure, which are capable of grain boundary sliding during plastic deformation. It has been shown that in the course of ECAP-Conform a crystallographic texture forms in a rod, which can be described as a combination of orientations of pyramidal {01 ‾1 2} <10 ‾1 0> and prismatic {10 ‾1 0} <01 ‾1 0> components. During ECAP-Conform sliding along base planes is hindered, which can be associated with lower processing temperatures of titanium in comparison with a conventional ECAP. |
full paper (pdf, 2080 Kb)