The Low Cycle Fatigue Behavior of a First Generation Single Crystal Superalloy CMSX-6 at 770 ℃

The investigation of the low cycle fatigue behavior of a first generation single crystal superalloy CMSX-6 were presented. Specimen of CMSX-6 alloy with standard heat treated were test by the fatigue testing machines. The study indicate the low cycle fatigue of CMSX-6 is about 965MPa at 770 ℃, R = 0 with a cycle number of 106. Subjected to periodic loads, the dislocation movement in the alloy is restricted to a small part of the crystal plane at the stress concentration area and intensive local slip occurs, resulting in plastic deformation in the local area, and the straight shape of the specimen side became crooked. SEM observation indicate that the fatigue cracks initiate from the internal microporosity of the specimen, and the transient fracture is formed after the crack propagation. The oxidation in crack propagation zone is serious, and the fatigue bands are not visible. Shear dimples were found at the transient fault zone.