Materials capable of withstanding harsh environments have the potential to enable a wide range of important technologies. A family of ceramic carbide and nitride materials referred to as MAX phases possess unusual and often unique sets of properties that combine some of the best attributes of ceramics and metals. These are light, stiff, stable and able to resist high temperatures like typical ceramics, but also damage tolerant, ductile at high temperatures and as readily machinable as metals. In addition, some of the MAX phases form protective layers when heated in air, that are extremely resistant to thermal shock, thermal cycling and chemical attack. This Designing Materials to Revolutionize and Engineer our Future (DMREF) award supports fundamental research to understand the process by which these protective layers in MAX phases are formed. This research will incorporate computational simulations and experimental synthesis and characterization to build the knowledge base for the accelerated development and design of MAX phase materials with outstanding mechanical properties for high temperature applications. Results of this project will foster application of MAX phases in power generation, energy conversion, transportation, aerospace and defense technologies. This project also provides specialized multidisciplinary training for graduate and undergraduate students on integrating materials informatics, modeling, atomistic computations and experiments in materials design.
Despite two decades of experimental studies on MAX phases, designing their optimal composition and microstructure has remained a challenge mainly because of the large number of possible compositions and microstructures, and a lack of robust physical models that relate their composition and microstructure to properties. The overall goal of this research program is to overcome those challenges and foster design of MAX phases for high temperature applications by: (1) developing physics-based predictors for the formation of protective alumina layers; (2) developing micromechanical models and identifying compositional/structural parameters that control intrinsic thermomechanical properties; (3) designing Bayesian calibration protocols for parameter identification; (4) implementing and deploying Efficient Global Optimization protocols for the efficient discovery of MAX phases with optimal thermomechanical properties and; (5) validating the proposed framework through material synthesis, characterization and thermomechanical testing. This will provide guiding fundamental knowledge and protocols to design optimal compositions and microstructures of the MAX phases for high temperature application.