THE CYCLIC DEFORMATION-BEHAVIOR OF CU SINGLE-CRYSTAL ORIENTED FOR DOUBLE SLIP

Copper single crystals oriented for double slip ([034] and [(1) over bar 17]) and single slip ([(1) over bar 25]) were cyclically deformed at constant plastic shear strain amplitude in the range 8 x 10(-5) less than or equal to gamma(pl) less than or equal to 1.4 x 10(-2). The initial cyclic hardening of the [034] crystal was found to be similar to that of the [(1) over bar 25] crystal, while the initial cyclic hardening rates of the [(1) over bar 17] crystal are significantly higher than those of [(1) over bar 25] and [034] crystals. The cyclic stress-strain (CSS) curve of the [034] crystal exhibits a plateau similar to that of the [(1) over bar 25] crystal, but the plateau ends at a relatively lower strain amplitude (gamma congruent to 4.3 x 10(-3)). The CSS curve of the [(1) over bar 17] crystal shows almost no plateau. The saturation shear stresses increase monotonously with Increasing gamma(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 gamma(pl) below 10(-3), and two types of deformation bands may form for gamma(pl) greater than 10(-3), which are different from those previously reported.