Effect of secondary orientation on room temperature tensile behaviors of Ni-base single crystal superalloys

The influence of secondary orientation and holes on the localization and the evolution of plasticity during room temperature tensile tests of thin wall specimens of a Ni-base single crystal superalloy were investigated. An ARAMIS system based on the digital image correlation technique was employed to in-situ observe the strain distribution on the sample surfaces, and an in-situ scanning electron microscopy was used to in-situ observe the slip traces development during tensile tests. For the smooth specimens, the tensile strength of<110>specimen is slightly higher than that of<100>specimen (<110>and<100>are the secondary orientations of the specimens). However, in the case of specimens with a hole in gauge section, detailed analysis indicates that 3-D tensile stress in the vicinity of the hole results in more slip systems initiated in<100>specimens, which may lead to stronger strain hardening. As a result, higher strength is obtained in<100>specimens with a hole.