Deformation-induced microstructural modification is utilized by several high-strain processing methods such as rolling, friction-stir-based processing, welding, or additive manufacturing. Consistent distribution of high density of crystallographic defects allows heterogeneous nucleation sites for nano-scale precipitation of intermetallic phases and often results in high-performing nanostructured alloys. The state of high defect density in the material also makes them highly susceptible to reactive gases, such as oxygen, present in the atmosphere. Atomic-scale studies on understanding deformation-induced defect formation and modes of diffusion, especially in the presence of reactive gases, are limited.
Investigation of fundamental mechanisms related to phase stability/transformations, and oxidation of metals and alloys under extended strain deformation processing, have been the core of my research in the past several years. This seminar will present insights into (a) the influence of high-strain deformation in modifying transformation pathways; (b) adding the compositional and phase complexity to the microstructural template to tailor the physical property; (c) integrating in-situ and ex-situ experimental characterization tools and using combinatorial approaches at multiple lengths and time scales to understand the effect defect density, thermal activation and environment on microstructural changes.
The experimentally observed variations in the transformation pathway are rationalized via the competition between the thermodynamic driving force and activation barrier for second-phase nucleation, coupled with the kinetics of the process. The microstructural variations that result from different phase transformation pathways are used to tune the multifunctionality of materials.