Correlation of grain boundary precipitate characteristics with fracture and fracture toughness in an Mg-8Al-0.5 Zn alloy

In the present work, the fracture and fracture toughness properties of the Mg-0.8Al-0.5Zn alloy have been studied. In view of this, four different aging temperatures were selected to vary the size and area fraction of grain boundary precipitates and the associated precipitate-free zones (PFZs) width. The results suggest that the precipitation state at the grain boundary plays an important role in deciding the exact mode of failure (i.e., intergranular or transgranular type). The role of precipitate characteristics in determining the fracture mode has been ascertained. Moreover, the significance of preferential deformation within PFZ regions has been evaluated using TEM. The correlation between the various microstructural features and fracture toughness value is established following the Hornbogen and Graf model. The measured values of fracture toughness are found to be in good agreement with the values predicted by the model.