Tensile behaviors and deformation mechanisms of a nickel-base single crystal superalloy at different temperatures

The tensile behaviors of an experimental nickel-base single crystal superalloy have been studied from room temperature to 1100 degrees C. Obvious work hardening during the tensile tests from room temperature to 760 degrees C has been observed. In contrast, at 900 degrees C and 1000 degrees C only a slight work hardening occurs. Furthermore, by using transmission electron microscopy (TEM), the microstructures of the alloy after tensile tests at various temperatures have been investigated. Detailed analysis demonstrates the stacking faults (SFs) presented in the gamma matrix at room temperature, 600 degrees C and 760 degrees C, which were seldom reported previously. These stacking faults are responsible for the appearance of stress jump (named steps) on the stress-strain curves. On the other hand, these stacking faults effectively prevent slipping of the dislocations and have a great contribution to work hardening. Apart from that, the stacking faults in gamma' precipitates from room temperature to 900 degrees C have also been observed. The interfacial dislocation networks at 1000 degrees C and 1100 degrees C cause a weak resistance to the slip dislocations because of the high flow stress. The a/3 < 121 > and a/2 (< 011 > type dislocations are of vital importance for plastic deformation and rupture of the experimental alloy. At last, the relation between deformation mechanisms and tensile behaviors has been reasonably explained. (C) 2014 Elsevier B.V. All rights reserved.