Cracking reasons of spray forming 7055 super high strength aluminum alloy forgings

A spray forming 7055 ultra-high strength aluminum alloy forging for an aviation wheel product cracked early in the static pressure test. Combined with the hot working forging process, heat treatment process and static pressure test conditions of the forging, the cracking reasons of the forging were analyzed by means of macroscopic observation, electrical conductivity test, mechanical property test, metallographic examination, microstructure observation, fracture analysis and finite element simulation analysis. The results show that the failure mode of static pressure test cracking of the forging belonged to one-time overload fracture. Due to the deep positioning hole and the right angle stress concentration at the root of the forging, cracks initiated at the root of the bolt positioning hole, and the streamline of the wheel forging at the sharp corner promoted the formation and propagation of the cracks. The failure strength of the forging hydrostatic test could be effectively improved by reducing the depth of the positioning hole, increasing the fillet of the circular arc transition at the root of the hole, and optimizing the heat treatment process to meet the acceptance requirements.