Thermal stability and annealing behaviour of ultrafine grained commercially pure titanium

Ultrafine grained (UFG) commercially pure titanium was fabricated by 8 successive passes of equal channel angular pressing (ECAP) via route BC. The deformed structure was studied by transmission electron microscopy (TEM). The material was then annealed at a range of temperature (450–600 °C) for up to 6 h. The microstructure evolution and the grain growth behaviour were investigated by electron back scattered diffraction (EBSD) technique. The UFG titanium was found to be thermally stable up to 450 °C. Based on the experimental results, the grain growth kinetics was characterized by calculating the grain growth activation energy (Q) and the time exponent (n). The value of Q was found to be close to the self diffusion activation energy of titanium, while n was found to be lower than the time exponent reported for grain growth in coarse grained pure titanium.