In situ electro-plastic treatment for thermomechanical processing of CP titanium

Titanium and its alloys have been used in a broad range of products such as biomedical implants due to their high specific strength, corrosion resistance, and biocompatibility. Improvement in microstructure and mechanical properties of commercially pure (CP) titanium is usually performed by cold rolling and controlled atmosphere heat treatment. However, this is an energy-intensive, expensive, and a multi-stage process to achieve the desired properties. Hence, to address these challenges, in this study, the effects of an in situ electro-plastic treatment (ISEPT) on the microstructure evolution of CP titanium have been studied. The deformation load and electric current in this treatment were applied in the same direction (in situ) to maximize the electro-plastic effect. Simultaneous electric current and strain application created a condition for dynamic recrystallization to occur at low temperature and under atmospheric conditions, thus reducing the cost and energy for manufacturing in a single process. The rapid heating and cooling prevented the oxidation of titanium to a large degree, eliminating the requirements for costly inert gas or vacuum. The results showed rapid recrystallization of CP titanium at 3.2 mm/s roller surface speed. Recrystallization led to a reduction in average grain size to 7 μm with 18% increase in microhardness. Pre-cold rolling of the CP-Ti structure enhanced grain refinement due to the introduction of dislocations and the applied electric current interactions. The SEM and XRD investigations revealed the relationship between the ISEPT treatment and the evolution of microstructure in CP-Ti. The effect of specimen geometry on the ISEPT was discussed.