Study of Thermal Stability of Ultra Fine-Grained Commercially Pure Titanium Wire Prepared in Conform Equipment

Titanium and its alloys are frequently used in many sectors, including the health care sector, where they outperform other materials. From the biocompatibility viewpoint, the preferred condition of these materials is ultrafine or nanostructured state. Processes based on severe plastic deformation (SPD) that are capable of producing microstructures with sizes of the order of nanometers are gaining importance these days. Their typical limitation is the small volume of material processed. One of available ways to enhancing the productivity is to combine the CONFORM continuous extrusion process with the ECAP method. This paper describes initial experience with this combined process in the CONFORM 315i machine, which is equipped with a specially-designed forming die chamber. Influence the number of passes through CONFORM machine on thermal stability was study by horizontal dilatometer and heat-flux calorimeter. The impact of deformation on the shift in recrystallization temperature of pure titanium was confirmed. The microstructure evolution and the grain growth behavior were investigated by electron back scattered diffraction (EBSD) technique. The deformed UFG titanium was annealed at a range of temperature (400-600 °C) for up to 6 h. The grain growth kinetics was characterized by calculating the grain growth activation energy Q and the time exponent n based on the experimental results for deformed material. Data for annealing temperatures of 550 and 600 °C allowed the values of the time exponent n = 0.19 and activation energy Q = 248 kJ/mol were calculated.