Simulation of correlated evolution of precipitates in Mg-Y-Nd alloys and the precipitation strengthening mechanism
As the lightest structural metallic materials, magnesium - rare earth (Mg-RE) alloys have received considerable attention worldwide for their large potential applications. However, their strength needs to be increased, which can be achieved through precipitation hardening. Understanding the formation of precipitates and their strengthening mechanism is critical for improving the Mg-RE alloys. In this project, we will reconstruct two models: a correlated evolution model combining the phase field approach, ab initio and phase diagram calculation, and a strengthening model based on the phase field dislocation model. With the correlated evolution model, we will be able for the first time to study Mg alloys with multiple precipitate phases. This model will be applied specifically to a Mg-Y-Nd based alloy strengthened by the β1 and β' phases. The two phases form a dumbbell structure. We will propose a formation mechanism for the dumbbell structure, which can explain the experimental observations. Influence of pre-existing dislocations on the shapes, formation and distributions of the precipitates will also be investigated. With the strengthening model, we will be able to analyze the contribution of different precipitate phases to the strength of the alloy, and the effects of shapes, distributions of the precipitates. This project will not only explain some fundamental questions in precipitation hardening, but also be beneficial for increasing the strength of alloys in industry.