Research on the microstructural evolution mechanism and impact toughness of Ti-17 alloy with an initial basket-weave microstructure

In this work, the microstructural evolution mechanism and impact toughness of Ti-17 alloy with an initial basketweave microstructure were systematically studied. Ti-17 alloys were rolled by 0, 20%, 40% and 60% at 860 degrees C, and afterward immediately aged at 600 degrees C for 8 h. The main evolved microstructural features were the globularization of the lamellar primary alpha phase (alpha p) and the precipitation of the lamellar secondary alpha phase (alpha s). The globularization fraction of alpha p raised, while the fraction of precipitated alpha s first increased and then decreased as the thickness reduction increased from 0% to 60%. The globularization behavior of alpha p originated from the combination of the alpha p recrystallization and the cutting of the beta phase. The alpha s precipitation was affected by dislocation density in the beta phase. In the thickness reduction range of 0-40%, the microstructural evolution of the alpha phase (alpha p and alpha s) enhanced impact toughness, which was largely attributed to the higher amount of precipitated alpha s. However, at the thickness reduction of 60%, the impact toughness sharply decreased due to the high globularization fraction of alpha p and the minor precipitation of alpha s negatively affected the crack propagation inhibition.