Enhancement of mechanical properties of grade 4 titanium by equal channel angular pressing with billet encapsulation

• Commercial purity Ti was processed by equal-channel angular pressing at a low temperature.
• This was made possible by encapsulation of a Ti billet in a Cu sheath.
• Extreme grain refinement and increase of strength to the Ti–6Al–4V levels was achieved.
• Commercial purity Ti can thus replace the alloy in medical implant applications.

Commercial purity titanium (Grade 4) was processed by encapsulation-aided equal-channel angular pressing. Encapsulation in a copper cartridge made it possible to carry out the process repeatedly, up to 8 passes, at a relatively low temperature of 300 °C. Extremely high values of yield strength and tensile strength close to record literature values for this titanium grade and matching, or even surpassing, the levels for conventional Ti–6Al–4V alloy were obtained. A bi-modal grain structure observed may be responsible for a favorable combination of strength and ductility the processed material exhibits.