EFFECT OF STRESS REVERSALS ON THE WORK-HARDENING BEHAVIOR OF POLYCRYSTALLINE COPPER

Flow behavior was determined under conditions where the loading direction is reversed after increasing amounts of prestress (or prestrain). The Bauschinger effect (defined as the response during the early stages of reverse flow) first increases and then saturates as the prestress is raised. In the same stress range, the reverse work hardening rate, theta //r, is higher than that determined from a continuous test theta //f. Beyond this stage, theta //r becomes less than theta //f. The difference DELTA theta equals theta //f- theta //r attains non-negligible values over an extended stress (strain) interval of reverse loading before it becomes equal to zero. Concurrently, the reverse flow stress sigma //r tends to saturate before it begins to rise again. The rearrangement of dislocation substructure that appears to take place in this stress (strain) interval is treated by employing a two-component composite model.