Failure analysis and Discussion on forging of a fuel gear pump shell

The crack is located in the middle of the shell and at the root of the processed 8-shaped hole. The plane of the crack is parallel to the forging axis and extends along it. The fracture characteristics of the original crack area are small dimples and impurity phases, and the fracture characteristics are the same as those of manual interruption. Therefore, the property of the shell crack is overload.

The main composition of the fracture is in accordance with the requirements of 2A14 aluminum alloy, and no abnormality is found; The hardness near the fracture meets the design requirements. Metallographic analysis shows that the deformation degree of the edge and center of the failure part is different, and the deformation of the center is larger. There was no significant difference in the microstructure deformation between the edge and the center of the intact parts. The above results show that the residual stress inside the failure part is greater than that outside, which is consistent with the residual stress detection results. At the same time, the crack is along the chain impurity phase in the middle region, and the chain distribution of impurity phase is unfavorable to the material properties.

Comprehensive analysis shows that the crack of the forging shell is related to the distribution of chain like impurity phase and larger residual stress.