Low-temperature fatigue behaviour and development of dislocation structure in aluminium single crystals with single-slip orientation

Abstract

Al single crystals oriented for single slip were cyclically deformed under constant plastic strain amplitudes between 1 × 10−3 and 5 × 10−2 at 77 K. Al single crystals showed hardening to saturation at all applied shear stress amplitudes. The resultant cyclic stress–strain curve (CSSC) showed a stress plateau in a range of plastic strain amplitude from 2 × 10−3 to 2 × 10−2. Surface observation revealed that multiple slip systems were active even at the strain amplitude in the plateau region. At plastic strain amplitudes corresponding to the plateau of the CSSC, persistent slip bands (PSBs) were formed parallel to the primary slip plane. In the PSBs, well-developed dislocation walls parallel to the {100} planes were observed. The microstructure in the PSBs was explained by the fact of multiple activation of the primary and critical slip systems. The above results indicate that the high stacking fault energy of Al is an important factor affecting the fatigue behaviour even at 77 K.