The mechanism of crack generation and propagation in the new casting alloy GH4151 during cogging

Based on the crack phenomena observed in an actual cogging experiment of the new as-cast GH4151 alloy, the mechanism of crack generation and propagation during cogging was studied by scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD). The results reveal that there were massive and spherical precipitates at the original grain boundary, large-scale holes at the edge of the precipitates and other areas, tiny pores near the grain boundary, and secondary microcracks along the grain boundary. These phenomena all promoted the generation and propagation of cracks. The fracture surface of the crack was determined as intergranular fracture, and local cleavage fracture was found to occur at the grain intersection. Moreover, the strain energy concentration at the grain boundary was evident, and the deformation of billets was found to primarily depend on grain boundary slip and grain rotation.