Kinetics of substructure changes in molybdenum single crystals in conditions of fatigue

Making use of an X-ray double-crystal spectrometer studied was the dislocation structure formed in the process of sign-variable deformation (extension-compression) of molybdenum monocrystals of two orientations: by approximately 9 deg deflection from direction <111> (monocrystal 1) and by approximately 2 deg deflection from < 123 > (monocrystal 2). The results obtained from the microroentgenographic study were compared with the fatigue durability and the kinetics of variation in the hysteresis loop width. It is pointed out that with comparable values of shear stress in the primary slip system crystals 2 exhibit a longer durability as compared to crystals 1 in the whole range of service durability since crystals 1 do not exceed the conventional fatigue limit (approximately 107 cycles), this being associated with relaxation processes taking place during fatigue phenomena in crystals 2, that are manifested in the formation of substructure due to the development of secondary and lateral slip