Microstructural evolution of equal channel angular drawn purity titanium at room temperature

Thin commercial-purity titanium (CP-Ti) wire was successfully acquired by equal channel angular drawing (ECAD) at room temperature with route Bc using a 90 degrees die at a relatively high drawing speed of 10 mm s(-1). The as-drawn CP-Ti wires were of good quality free of cracks and segmentation on their surface. The grain size of CP-Ti was reduced from -32 mu m for the as-annealed wire to similar to 700 nm for 12-passes equal channel angular drawn wire. The grain experienced transition from microband to thin lath and to equiaxed subgrains with the increment in drawing passes. Face-centered cubic (FCC) phase was triggered obviously to accommodate the large shear strain induced by ECAD at the drawing rate of 20 mms(-1). The thickness of the FCC phase increased with an increase in drawing passes, and no equiaxed subgrains were formed in CP-Ti. Accordingly, the drawing speed significantly affects the deformation mode and microstructural evolution of CP-Ti during ECAD. A lower drawing speed provides a longer time for the structure recovery, thus resulting in the occurrence of dynamic recovery when ECAD was performed at room temperature. Additionally, {10 (1) over bar2} tension twinning and {11 (2) over bar2} compression twinning occurred simultaneously to accommodate ECAD shear deformation. The success in processing CP-Ti rods at room temperature through multiple passes of ECAD provides a new perspective to efficiently fabricate ultrafine grained small-sized materials continuously. (C) 2019 Elsevier B.V. All rights reserved.