Insight into the low cycle fatigue deformation mechanisms of minor element doping single crystal superalloys at elevated temperature

The roles of minor elements, usually as grain-boundary strengtheners, in the fatigue properties of single crystal (SX) superalloys have not received adequate attention. Our study reveals that both C and B remarkably increased the stress amplitude, while reduced the cyclic hysteresis energy, under the condition of approximate low cycle fatigue (LCF) lifetime at 980 ºC. In terms of the enhanced fatigue stress, it is considered to be associated with the interstitial solid solution strengthening. Based on the analysis of deformation microstructure, the improved fatigue deformation resistance can be ascribed to the formation of slip bands and a<010> superdislocations in C-containing alloys, whereas, B additions triggered the denser dislocation-tangle at the γ/γ' interface and the homogenization of overall dislocation distribution.