Host: The Japan Society of Mechanical Engineers
Name : [in Japanese]
Date : December 22, 2018 - December 24, 2018
The influences of cross slip activity on the low-cycle fatigue behavior and dislocation structure of pure Al single crystals were systematically investigated. Plastic-strain amplitude controlled fatigue tests were conducted at room temperature (RT) and 77 K using pure Al single crystals bearing a single-slip orientation but having a different value of the Schmidt factor (SF) of 0, 0.14 or 0.24 for a cross-slip system. Low-cycle fatigue behavior at RT varied greatly depending on the values of SF. The specimens with SF = 0.14 and 0.24 exhibited initial hardening, softening and then secondary hardening. While no softening behavior was observed in the specimen with SF = 0. Microstructural observations revealed that cell structure was developed in all the specimens. The high density of dislocations on the crossslip planes was confirmed within the cells formed in the specimens bearing non-zero SF. On the other hand, dislocations on the cross slip panes were rarely visible in the specimen with SF = 0. Shear stress amplitudes showed cyclic hardening to saturation at 77 K, regardless of SF values. After the stress saturation, well-developed persistent slip bands (PSBs) and matrix vein structure coexisted in all the specimens. The dislocation walls were regularly aligned perpendicular to a primary slip direction in PSBs, and their average spacing was about 0.4 μm. It can be concluded that the SF-value dependent fatigue behavior of specimens at RT is attributed to the activity of cross slip system.
