Simulation Of Grain Growth In AZ31Mg Alloy Influenced By Second-phase Particles In Different Geometric Morphology

Magnesium alloy as the lightest structural material has been paid much attention in recent years due to its excellent properties. Magnesium alloy has been widely used in automotive, aerospace,3C products and other fields in industry. AZ31alloy which is one of the widely used commercial deformation magnesium alloys has been chosen as simulation sample in this research. For the solubility of Al and other elements in Magnesium alloy is low, the effect of solution and aging strengthening is not good. Therefore, we explore a potential way to improve mechanical properties of AZ31alloy by refining grain size through introducing second-phase particles. This study will provide theoretical guidance to introduce second-phase particles by compound addition or in-situ reaction synthesis in AZ31alloy from microstructural level.A Phase field model to simulate grain growth has been studied to select the right input parameters with proper physics meaning under realistic spatial and temporal scales. Then it has been validated by experimental results with different size, shape, volume fraction and distribution of second-phase particles in AZ31alloy.The simulation shows that under the same shape of second-phase particles, the higher volume fraction of particles, the stronger pinning effect of grain boundary is, and the smaller stable grain size. If the volume fraction of second-phase particles is fixed, the spherical particles has a critical size. When the particle size are smaller than the critical value, the larger size leads to a stronger pinning effect in grain boundary; otherwise, the larger size of particle makes pinning effect weaker. When the morphology of particles is different and the volume fraction of particles is less than2%, the effect of refining grain from strong to weak is sphere, ellipsoid and rod; respectively, by means that the pinning force is inversely proportional to the aspect ratio of particles. However, when the volume fraction is higher than4%, the effect of refining grain from strong to weak is rod, ellipsoid and sphere; respectively, Also, we explore the effect of particle distribution during grain growth. In our simulation, when we set10%,30%,50%,80%and100%segregation of particles on the boundary, the results show that as the percentage of particles segregation increases, the grain is more refining, especially, in low particles volume fraction. However, this effect becomes weaker as the volume fraction is less than60%.The simulation results proves that the microstructural evolution of AZ31alloy is in agreement with the Zener theoretical observation.The study will facilitate to understand the mechanisms of grain growth associated with the second-phase particles strengthening. Moreover, it refers to an important way to precisely control the amount of the second-phase particles added to refine grain of AZ31alloy in order to improve its properties.