Strengthening of Titanium by Equal Channel Angular Pressing - Impact on Oxide Layer Properties of Pure Titanium and Ti6Al4V

Equal channel angular pressing (ECAP) as a method applicable to large samples for strengthening metallic materials via severe plastic deformation has recently attracted considerable interest. For biomedical applications, ECAP-treated pure titanium is a promising alternative for implants subjected to high mechanical loads as it contains no potentially cytotoxic alloying elements. The consequences of an ECAP treatment for the physico-chemical properties of the air formed passive layers of pure or alloyed titanium, which are of the utmost importance for the biological response to these materials, are studied here for the first time. This includes mechanical, electron microscopic, and electrochemical investigations in protein containing media to study the reactions that occur immediately after implantation in the phase boundary between implant and biological system. The ECAP treatment results in a positive shift of the flatband potential and a particularly strong increase of the donor density for the native oxide layers. This is associated with increased electronic conductivity of the oxide layers under anodic polarization.