Data rich imaging approaches assessing fatigue crack initiation and early propagation in a DS superalloy at room temperature

The behavior of anisotropic fatigue short crack initiation and propagation for a directionally solidified superalloy CM247LC at room temperature

“…The results suggest a higher local strain at the crack initiation sites in the LR specimen, consistent with the higher strain amplitude experienced by the sample. The crack initiation sites of the RR specimen are similar to the RL specimen, as already reported in Tan et al 25 …”

“…Previous research 25 shows that the DS superalloy studied contains large amounts of carbides and pores co‐segregated at the inter‐dendritic regions. To clearly determine the interactions between these microstructure features and crack initiation behaviors, the fracture surface was carefully examined under SEM, using a Robinson‐type backscatter detector (BED‐C).…”

“…Transgranular slip‐band cracking is largely observed in the vicinity of the main crack of the LR sample (Figure 6A,B), while more intergranular cracks are initiated from the large carbides at the GBs of the RL specimen. For the RR specimen, 25 the secondary crack initiation behaviors are closely related to the plastic zone of the main crack. With the increase of the main crack length, the plastic zone of the crack tip is enlarged and the secondary crack initiation sites transfer from large carbides or pores to the slip bands.…”

“…The DS superalloy CM247LC was provided by the General Electric Power Company, with the composition listed in Table 1. Subsequently, the block received a commercially proprietary heat treatment comprising a solution heat treatment at time steps of 1221°C, 1232°C, and 1246°C, respectively, followed by dual aging heat treatments at 1080°C and 870°C 25 …”

“…The DS superalloy CM247LC was provided by the General Electric Power Company, with the composition listed in Table 1. Subsequently, the block received a commercially proprietary heat treatment comprising a solution heat treatment at time steps of 1221 C, 1232 C, and 1246 C, respectively, followed by dual aging heat treatments at 1080 C and 870 C. 25 To obtain the Young's modulus and yield stress data for specimens with columnar grains aligned with and transverse to the loading direction, tensile tests were performed for the specimens shown in Figure 1A at a strain rate of 1 Â 10 À4 s À1 . The sample with columnar grains aligned along the loading direction is termed as the longitudinal (L) sample, while the other with grains transverse to the loading direction is termed as transverse (T).…”