“Towards deliberately dynamic materials: Materials solutions for extreme environments”
Faced with longer service lifetimes, higher operating temperatures, more complex loading configurations, and aggressive environments, reliable operation of many key technologies hinges upon the durability of materials or material systems. In these extreme environments, understanding the evolution of material properties may be even more important than the initial performance of the material. By identifying and understanding service-induced materials evolution, it may be possible to capitalize on this understanding in such a way that enables materials to adapt and improve in their environment, rather than degrade. But in the laboratory, it can be very difficult to replicate the combination of stimuli that define a service environment as “extreme.” Instead we must leverage creative experimental platforms that will ultimately allow for the discovery and integration of the competing driving forces responsible for materials evolution. This is the pathway to realizing a new class of deliberately dynamic materials. My research group has taken the first steps towards this vision by employing wide-ranging materials processing capabilities and advanced characterization tools to create and observe several dynamic model material platforms. In this talk, I will specifically focus on the use of unique defect structures in nanocrystalline, nanotwinned Ni-based alloys. I will show how we revealed the equilibration pathway for a complex precipitation strengthened alloy by manipulating the defect population. We can directly apply this insight to predict and understand the behavior of conventionally processed alloys subjected to exceedingly long service lifetimes. I will also use this model material platform to demonstrate how we promoted preferred oxide scales by selectively preserving important diffusion pathways, which can be applied to microstructural engineering of alloys in corrosive or oxidizing environments. Overall, this nanocrystalline, nanotwinned thin film model material platform has provided impactful perspectives on fundamental mechanisms as well as actionable strategies for materials in extreme service conditions.
