Fatigue tests were carried out on samples of titanium VT1−0 and zirconium alloy Zr−1 wt % Nb in the ultrafine-grained, fine-grained and coarse-grained states in a gigacycle fatigue regime. It was found that the formation of an ultrafine-grained structure led to an increase in the fatigue limit in the gigacyclic region (109 cycles) by 1.3 times for titanium and 1.7 times for zirconium alloy when compared to the fine-grained and coarse-grained states. An evolution of the temperature field for 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 in all types of structural states was accompanied by an initiation and expansion of a heat source in a local volume of samples which has a significant impact on the fatigue strength. The increment of the maximum temperature 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 states. This fact indicates a qualitative change in the mechanism of energy dissipation which is associated with characteristic features of the ultrafine-grained state. When comparing the dynamics of 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 covered a considerable volume of the sample in the process of fatigue tests in case of ultrafine-grained state, whereas in case of coarse-grained and fine-grained states the growth of thermal energy was localized in the gauge area of the sample.
ASJC Scopus subject areas
- Materials Science(all)