High strength ultra-fine grained titanium produced via a novel SPD processing route

This work focuses on the mechanical properties and on the deformation behavior of commercially pure (CP) Ti processed via a novel SPD route. The material was subjected to equal-channel angular pressing at 450°C for 8 passes using the processing route Bc. Then the rods were subjected to swaging and drawing with the total accumulated strain of ∼80%. The processed CP Ti has a homogeneous microstructure consisting of grains and subgrains elongated along the rod axis. The average width of grains/subgrains is 200 nm and their length is 200 - 600 nm. Mechanical properties and deformation behavior of the UFG CP Ti in both longitudinal and transversal directions are studied at room temperature. It is shown that in the longitudinal direction, the UFG CP Ti has a superior strength (yield strength of 1220 MPa and ultimate tensile strength of 1280 MPa), but a low uniform elongation (∼3.7%). In the transversal direction, the strength properties are significantly lower; a strong scatter of the values of uniform elongation and elongation to failure is found. Analysis of deformation relief in the longitudinal specimens shows a homogeneous plastic deformation before necking and micro shear banding within the necking area. In the transversal specimens, the micro cracking results in significant scatter of the values of the uniform elongation / elongation to failure.