Effect of cold rolling reduction on grain growth kinetics of TB8 titanium alloy during annealing heat treatment

The effect of cold rolling reduction on grain growth kinetics of TB8 titanium alloy, during annealing heat treatment, is investigated systematically. The alloy was cold rolled with reductions of 20%, 40% and 60%, followed by annealing process at 750 degrees C(alpha/beta field), 800 degrees C (close to beta transition point) and 850 degrees C (beta field) during various time spams. Results show a very fast grain growth of cold rolled sheets, at the initial stage of annealing, followed by a gradual decrease, as the holding time increases. Also, the grain size uniformity was significantly affected by reduction and annealing temperature. It was shown that a better uniformity in grains size can be achieved by a larger reduction. During the annealing, the higher temperature contributed to grain size uniformity, before the point of 120 min. However, the relatively good uniformity of grains size was achieved at 800 degrees C, after 120 min. The growth exponent and the activation energy of grain growth have been calculated. The grain growth time exponent was positively influenced by annealing temperature, while the cold rolling reduction had little effect on it. However, larger reduction will lead to lower activation energy of grain growth, whereas, during annealing, the activation energy will increase along the holding time.