Influence of the helical rolling and controlled cooling to impact toughness of titanium alloy Ti-6Al-3Mo

The paper studies the evolution of the structure, phase composition, and impact toughness of the Ti-6Al-3Mo titanium alloy after two types of processing, one of them is included heating and hot helical rolling with quenching in water (mode I). The additional air quenching is used between the rolling and quenching processes in mode II. This approach with combining two cooling stages (in air and in water) of the alloy makes possible to control the recrystallization time and form a gradient structure over the cross-section of the bar stock. The processing of titanium alloy according to mode I lead to decrease of impact strength. The addition of air-cooling stage (in mode II) leads to insignificant decrease hardness and increase toughness of alloy. The treatment by mode I and II of the titanium alloy lead to formation of the structure which contain large grains of the primary α-phase in thin-plate structure of the secondary α-phase in the β-phase. It is shown that the obtained structure states of alloy affect to crack propagation under impact loading and changing the amount of energy which spent to the complete destruction of the samples.