A model for predicting fracture toughness in overaged 7000 alloy forgings

Abstract

An attempt to develop a multiple micromechanism-based model for predicting plane-strain fracture toughness, KIc, of overaged 7000 alloy forgings has been made. The proposed model reveals the quantitative relations between the fracture toughness, fraction of the main fracture modes and parameters such as volume fraction, size and density of differently sized second-phase particles and precipitate-free zones. The new model is validated by the present quantitative data of microstructural and fractographic analysis performed along with mechanical tests on hot-forged plates subjected to the T73 temper. The relative parameters changed by the compositional variations were determined in the R-L and L-R orientations. It was found that the predicted KIc values well represent the tendency of fracture toughness change. The new model provides better agreement for the case of dominant transgranular fracture mode represented in the R-L orientation. .