Effect of the Texture of the Ultrafine-Grained Ti-6Al-4V Titanium Alloy on Impact Toughness.

In this work, the strength properties and impact toughness of the ultrafine-grained (UFG) Ti-6Al-4V titanium alloy produced by severe plastic deformation (SPD) in combination with upsetting were studied, depending on the direction of crack propagation. In the billets processed by equal-channel angular pressing (ECAP), the presence of anisotropy of ultimate tensile strength (UTS) and ductility was observed, conditioned by the formation of a metallographic and crystallographic texture. At the same time, the ECAP-processed UFG alloy exhibited satisfactory values of impact toughness, ~0.42 MJ/m. An additional upsetting of the ECAP-processed billet simulated the processes of shape forming/die forging and was accompanied by the development of recovery and recrystallization. This provided the "blurring" of texture and a reduction in the anisotropy of UTS and ductility, but a difference in impact toughness in several directions of fracture was still observed. It is shown that texture evolution during upsetting provided a significant increase in the crack propagation energy. The relationship between microstructure, texture and mechanical properties in different sections of the material under study is discussed.