Processing and characterization of nanostructured Grade 2 Ti processed by combination of warm isothermal ECAP and extrusion

Abstract

In this study, combined multi pass equal channel angular pressing (ECAP), and subsequent warm extrusion at different temperatures are performed on commercial purity titanium. Mechanical and microstructural evolutions are then investigated. Since it was observed that the four passes ECAP processed sample showed the best strength and reasonable elongation, this sample was selected for studying the extrusion temperature effects on the structure and mechanical properties of Grade 2 titanium. Therefore, the 4th passes ECAP processed sample was extruded at different temperatures of 300°C, 350°C, 400°C, 450°C and 500°C. The result revealed that the best mechanical properties were achieved from the specimen processed by four passes ECAP followed by warm extrusion at 300°C. The strength, and hardness of this sample were considerably improved in comparison with that of the unprocessed sample. Also, its ultra-fine grained and nanograined microstructure were homogeneous, with a grain size ranged from 40 to 200nm with an average grain size of about 123nm. It was seen that the mechanical properties of some samples after applying this combined process (ECAP + warm extrusion) are comparable with those of Grade 5 titanium which is commonly used in medical applications but contains alloying elements that are toxic to human health.