The Role of Microstructural Defects in Grain Growth Behavior

 A basic scientific understanding of microstructural evolution is of the utmost importance in materials science because control of the microstructure allows for improving the bulk properties of a material. For ceramics, this includes a thorough understanding of the role of defects on grain growth behavior. This work examines the connection between porosity and abnormal grain growth. The findings of this work allow for better microstructural control of engineered materials and provide useful insight that can improve grain growth models. Calcia doped alumina is used as a model ceramic because it is a well-studied system that exhibits abnormal grain growth, but for which many questions still exist. Controlled porous microstructures are fabricated using polymer microspheres and the grain growth behavior is characterized. Results indicate that large pores can have a significant effect on the initial development of abnormal grains. Three-dimensional microstructural characterization of abnormal grains in alumina is reported for the first time and shows that abnormal grains preferentially develop near large pores. Once developed, a population of abnormal grains can grow unhindered by the large pores, occasionally trapping the large pores within the grains. The combined findings provide a broader understanding of the interactions between large pores and abnormal grains which will allow for better control of these defects and improve the ability to predict abnormal grain growth behavior in complex systems.