A TEM STUDY OF DISLOCATION-STRUCTURES IN FATIGUED CU-16 AT-PERCENT AL SINGLE-CRYSTALS

Dislocation structures in fatigued Cu-16 at.% A1 single crystals were studied by TEM as a function of total strain amplitude and stress level. The results show that planar arrays of primary dislocations are preserved at all stages of cyclic deformation. With increasing stress level, the density of both primary and secondary dislocations increases and the spacing of the activated primary slip planes decreases. At all stages of deformation, primary edge dislocations dominate the structure, forming dipolar and multipolar arrays which sometimes show evidence of intersection along the traces of the cross slip planes. Primary screw dislocations are rarely observed to form multipoles. Numerous small prismatic loops are formed at the higher stress levels. Dislocation behavior during cyclic deformation, especially concerning strain localization, is discussed in comparison with that of copper. © 1990.