Comparison of low-cycle fatigue behaviors between two nickel-based single-crystal superalloys

The deformation mechanisms of nickel-base single-crystal superalloys containing 3 wt.% Re (3Re) and without Re (0Re) were systematically investigated in the temperature range from room temperature to 900 °C. At all testing temperatures, the alloy 3Re showed higher stress amplitudes and longer fatigue lives. With increasing temperature, slip mode gradually changes from planar to wavy slip. Dislocation climb and cross-slip, even by-passing became dominant deformation mechanisms of the two alloys and the addition of Re further reinforced this trend. In this process, the deformation homogenization became dominant, which resulted in the transition of cracking mode from shear fracture to normal fracture. At low temperature the specimen eventually cracks along the slip bands by shear, but at high temperature the specimen cracks by normal and shows mode I cracking.