TENSION/COMPRESSION ASYMMETRY IN CREEP BEHAVIOR OF A Ni-BASED SUPERALLOY

Orientation and temperature dependence of yield stress or CRSS (Critical Resolved Shear Stress) and tension/compression anisotropy of the yield stress or CRSS have been shown by Shah and Duhl (1), Heredia and Pope (2), and Miner et al. (3). Tension/compression asymmetry in the yield strength of Ni-based superalloys has been explained in terms of the “core width effect” (4). Shah and Duhl (5) observed the tension/compression asymmetry in creep deformation, which is similar to that observed in the yield strength, and indicated that it can be attributed to cross slip and dislocation core-constriction mechanisms associated with octahedral slip. However, little is known about the mechanism of tension/compression asymmetry in creep. In the present study, single crystals of a Ni-base superalloy were subjected to tensile and compressive creep tests. Tension/compression asymmetry in creep behavior was examined in detail for each orientation.