A new methodology for habit plane and orientation relationship prediction in precipitation strengthening of magnesium alloys

A new approach is presented, integrating the maximum atomic matching on the habit plane and reduced interfacial energy, to predict the orientation relationships (OR) and habit planes of precipitates in magnesium alloys. Understanding these ORs and habit planes is essential, as they directly govern the morphology, distribution, and interaction of precipitates with dislocations, which in turn influence the precipitation strengthening of magnesium alloys. The underlying hypothesis of this framework considers the habit plane or broad plane formed during precipitation reactions to be a singular interface. Using Al₂RE precipitation in Mg-Al-RE alloys as an illustrative example, we employ theoretical and first-principles calculations to predict the OR and habit planes of precipitates, with lattice mismatch and interfacial energy guiding the determination of the preferred OR and habit planes. Our predictive results reveal three potential orientation relationships and habit planes in Al₂RE/Mg alloys. Furthermore, the interfacial energies result reveals that the preferred OR and habit plane is [1¯100]_Mg/[011¯]_Al2RE; (0001)_Mg/(111)_Al2RE. Additionally, first-principles calculations reveal a preference for hollow close-packed configuration (HCP) in the interfacial atomic structure. The predicted ORs and habit planes for Al₂Gd/Mg alloys are consistent with experimental results, indicating that our method can predict the orientation relationship and habit plane of the precipitation strengthening of magnesium alloys.