Effect of surface recrystallization on the low cycle fatigue behavior of directionally solidified superalloy DZ4 by in-situ SEM studies

摘要

The effect of recrystallization on the low cycle fatigue life of DZ4 directionally solidified superalloy was investigated for specimens with three different recrystallized layers, which were generated by shot peening (0.1 MPa, 0.3MPa and 0.5MPa respectively) and a subsequent annealing heat treatment. The fatigue life showed a decrease for recrystallized specimens with shot-peening of 0.1 MPa and 0.3 MPa, and an unusual increase for that of 0.5MPa, in comparison with the original DZ4 specimen. In-situ SEM observations were performed on the short crack growth behaviors for both original and recrystallized specimens, which revealed the fracture mechanism and the interaction with microstructure. Quantitative analysis of fatigue crack growth rates rationalized the influence of recrystallization on the low-cycle fatigue life of DZ4.