The cyclic deformation behavior of Cu single crystal oriented for double slip

Abstract

Copper single crystals oriented for double slip ([034] and [ 1 117]) and single slip ([ 1 25]) were cyclically deformed at constant plastic shear strain amplitude in the range 8 × 10 −5 ⩽ γ pl ⩽ 1.4 × 10 −2. The initial cyclic hardening of the [034] crystal was found to be similar to that of the [ 1 25] crystal, while the initial cyclic hardening rates of the [ 1 17] crystal are significantly higher than those of [ 1 25] and [034] crystals. The cyclic stress-strain (CSS) curve of the [034] crystal exhibits a plateau similar to that of the [ 1 25] crystal, but the plateau ends at a relatively lower strain amplitude ( γ pl ≌ 4.3 × 10 −3 ). The CSS curve of the [ 1 17] crystal shows almost no plateau. The saturation shear stresses increase monotonously with increasing γ pl. The above mechanical behaviors are in accord with the strength of dislocation interactions between different slip systems. Surface observation revealed that for the double slip oriented crystals, secondary slip is inactive for γ pl below 10 −3, and two types of deformation bands may form for γ pl greater than 10 −3, which are different from those previously reported.