MECHANICAL PROPERTIES OF COMMERCIALLY PURE TITANIUM GRADE 2 AFTER SEVERE PLASTIC DEFORMATION

Mechanical properties and microstructures of commercially pure titanium (CP-Ti) developed by a newly designed multi-pass equal channel angular pressing (ECAP) process and cold drawing were investigated. The ECAP apparatus was developed in order to improve the efficiency of common ECAP and the performance of finished products. A much stronger CP-Ti billet was produced by using the proposed processes. As shown in the results, a severe plastic deformation occurred in the material by means of continuous shear deformation during the radical bending process through a repeated route. The resulting mechanical properties, such as yield and tensile strength, were improved thanks to the grain refinement that is connected with the Hall-Petch theory. Moreover, cold drawing was conducted to produce a cylindrical type bulk material by using the ECAP. Microstructural refinement with improvement of mechanical properties was attributed to this additional plastic forming process. It was found out that the finished products developed by the multi-pass ECAP and cold drawing processes had therefore remarkably hardened, and achieved the ultimate tensile strength of CP-Ti 397.2 MPa, compared to initial strength of 716.3 MPa, with significant refinement of the microstructure.