材料期刊网

Smooth and notched specimens of single crystal superalloy DD32 were subjected to rotary bending high-cycle fatigue (HCF) loading at different temperatures. The experimental results demonstrate that fatigue strengths of the smooth and notched specimens reach the maxima and the minimum notch sensitivity displays at 760 A degrees C. DD32 alloy exhibits excellent HCF properties compared to SRR99 alloy under the same test condition. As for the smooth specimens, slip bands moving through gamma and gamma' phases as well as dislocation bowing are the main deformation modes. As for the notched specimens, the deformations are carried out by dislocation loop bowing and shearing of PSBs mode at intermediate temperatures; at 900 A degrees C, the minimum fatigue strength results from dislocation climbing deformation and the degradation of gamma' precipitates. The fine secondary gamma' precipitates advantage the recovery of dislocations and further deformation of the fatigue specimens.