Failure mechanisms of titanium VT1-0 and zirconium alloy E110 in ultrafine-grained, fine-grained and coarse-grained states under cyclic loading in gigacycle regime

摘要

Fatigue tests were carried out for the samples of titanium VT1-0 and the Zr-1 wt. % Nb zirconium alloy in ultrafine-grained, fine-grained and coarse-grained states in the gigacycle fatigue regime. It was found that the formation of the ultra-fine grained structure in titanium and zirconium alloys leads to an increase in the fatigue limit of titanium by 1.3 times and the zirconium alloy by 1.7 times in the gigacyclic region (10*9 cycles) when compared to the fine-grained and coarse-grained states. The evolution of the temperature field for the titanium and zirconium alloy samples in various structural states in the process of cyclic loading was studied by the method of infrared thermography. It was shown that the process of cyclic deformation for all types of structural states is accompanied by the onset and expansion of the heat release center in the local volume of samples and has a significant impact on the fatigue strength. The maximum temperature increment on the surface of ultrafine-grained samples of titanium VT1-0 and zirconium alloy Zr-1 wt. % Nb is significantly lower than that for the fine-grained and coarse-grained state. This fact indicates a qualitative change in the energy of the mechanism absorption dissipation which is associated with the ultra-fine-grained state features When comparing with the dynamics of changes in thermal fields for the titanium and zirconium alloy samples in coarse-grained, fine-grained and ultrafine-grained states. It was found that the energy dissipation zone covers a significant amount of the sample in the process of fatigue tests for the case of ultrafine-grained state, whereas in the case of coarse-grained and fine-grained state, the growth of thermal energy has a localized character in the active zone area of the sample.