The Influence of Helical Rolling and Controlled Cooling on Impact Toughness of Ti-6Al-3Mo Titanium Alloy

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. Mode I consists of heating and hot helical rolling, followed by quenching into water. In mode II, an additional air quenching is used between the rolling and quenching processes. This approach, combining two alloy cooling stages (in air and in water), makes it 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 leads to a decrease of the impact strength. An addition of an air-cooling stage (in mode II) leads to an insignificant decrease in the hardness and an increase of the alloy toughness. The treatment of the titanium alloy by modes I and II results in the formation of a structure containing large grains of the primary alpha-phase in a thin-plate structure of the secondary alpha-phase in the beta-phase. It is shown that these structural states of the alloy affect the crack propagation under impact loading and change the amount of the energy spent on the complete failure of the samples.