The dislocation structures in Ti-5Al-5%V, which resulted from cyclic-strength and crack-propagation resistance tests (symmetrical tension-compression loading, 100Hz to 10kHz), were studied. A comparative analysis was made of the effect of the loading frequency upon the evolution of the dislocation structure during fatigue-damage accumulation, and in the fracture zone during fatigue-crack propagation. It was shown that, under these 2 loading conditions, the plastic deformation micro-mechanisms adapted themselves to the loading rate. In the first case, this was due to the fact that a decrease in the activity of Frank-Read sources under high-frequency loading was compensated by a more marked deformation of the α-phase as a result of the formation of stacking faults. In the second case, a high level of local stresses activated cross-sliding and the formation of a honeycomb structure in the α and β phases. The elements of this structure decreased in size with increasing loading frequency. The incompleteness of relaxation processes during high-frequency cyclic loading was off-set by the deformation of boundary volumes which were initially present in the α-phase of twins.

Dislocation Structure of VT22 Titanium Alloy in Cyclic Loading with Various Loading Frequencies. T.Y.Yakovleva: Strength of Materials, 2000, 32[4], 331, 337-8