The secondary orientation effect of single crystal superalloy thin-wall specimens at 850 °C with [001] primary orientation

An interesting phenomenon is found in Nickel-based single crystal superalloy thin-wall specimens which have the same [001] primary orientation and different secondary orientation with [100], [210], and [110] at 850 °C. Generally, the testing of cylindrical samples exhibits similar creep and tensile properties regardless of their vertical orientation distribution due to the circumferential symmetry of their geometric structure. However, the 850 °C experimental results of thin-wall specimens with the same [001] primary orientation show a significant difference in tensile ductility and creep life when the secondary orientation is different. The mechanism of the secondary orientation effect is completely discussed by combining experiment, digital image correlation (DIC), and finite element modelling (FEM), which result from the strengthening effect of Lomer-Cottrel dislocations and the ability to coordinate plastic deformation in tensile, the shrinkage rate of cross-section caused by the single slip system ({111} <11-2>) and deviation from [001] with a small angle in creep.