Exploring avenues for tailoring the stability of hierarchical microstructures in high-temperature alloys

Understanding phase separation phenomena enables tailoring microstructures of high-temperature structural materials to develop better materials with improved properties. High resolution characterization techniques are used to understand the link between structure-property relationships and the 3D nanochemistry of hierarchical microstructures in high temperature structural materials. Hierarchical microstructures form when additional g particles form within g’ precipitates and pose a novel concept to strengthen high-temperature structural materials. However, these g particles are metastable and two possible metastability pathways have been indentified: (1) continuous growth and split of g’ and (2) Growth and dissolution, both resulting in a loss of the strengthening effect. 

         This talk presents how high-resolution characterization techniques such as TEM, APT and synchrotron XRD are used to gain insight into microstructural behavior and phase stability. The combined results inform alloy design strategies to tailor fundamental properties of g particles to enhance their temporal stability and thereby retain the strengthening effect. APT offers unique insights into the 3D nanochemistry of phases in hierarchical microstructures with  g’ precipitates only ~100 nm in size and nanoscale g particles (~8 nm). The results suggest that by phase targeted alloying, supersaturation and evolution of phase separation can be controlled to tune the properties of such materials. To create new materials strengthened by hierarchical micrsotructures, the phase stability of g particles needs to be enhanced.