Fatigue failure stages of VT1-0 titanium in different structural states. Study by acoustic emission method

The paper studies the kinetics of fatigue damage accumulation in VT1-0 titanium by the acoustic emission (AE) method. Technical grade titanium VT1-0 in various structural states was tested under cyclic bending. Submicrocrystalline Ti-specimens (SMC, with subgrain size of 200–300 nm) were fabricated by equal channel angular pressing (ECAP) from polycrystalline titanium. Ingots with ultrafine grain structure (UFG, with structure element size of 1–2 µm) and coarse grain structure (CG, with structure element size of 20–30 µm) were prepared by annealing at different temperatures. Fatigue stages were identified by analyzing the AE signal parameters with their classification by the source type (dislocations, micro-and macrocracks). It was revealed that the specimens with a smaller grain size are of higher fatigue durability, while AE signals at the stages of yielding and microcracking are detected later because of their low energy.