Multiscale thermodynamics: From the atomic world to the real life application, how to get it all?

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Metallic materials such as aluminum alloys, nickel super-alloys and steel are used in a panoply of high performance applications in our modern societies: they are used in cars, in aircrafts, in bridges, in engines. Depending on the application, their high specific mechanical properties, their potential resistance to high temperature in service or their resistance to highly corrosive environment might be one of the several reasons why they are preferred to other materials. The high recycling potential of most metals and alloys is also an important aspect to consider when choosing the ideal material, especially in the aerospace and automotive industries where metallic alloys compete with composite materials.There exist several processing routes to elaborate metallic alloys and as many to transform them into metallic products such as beams, bolts, frames, shafts and sprockets. The vast majority of the metallic materials will evolve during their useful life. Some materials will corrode and their surface composition will change; some materials will experience dynamic precipitation of nanoparticles and will harden; while some other will see their bulk microstructure evolves by the effect of high temperatures. The driving force for all these phenomena is linked to the free energy difference between the actual state of a material and its equilibrium state. In fact, a material that reached its equilibrium state should not evolve anymore as long as the equilibrium conditions are not changed. For that reason heat treatments that relax metallic materials are typically used to ensure their stability in service.As highlighted here, the microstructure of a material will modulate its thermo-physical properties. Being able to predict the initial microstructure of a material as well as its evolution in service are two fundamental aspects scientists and engineers are trying to obtain from numerical simulations. All the available numerical approaches that model the microstructural evolution of materials require a key ingredient which is the precise evaluation of the thermodynamic driving force.This research program is intended to provide the next generation of thermodynamic models of metallic solid solutions that will account for all the fundamental energetic contributions that are the atomic vibration, the chemical environment surrounding each atom and the chemical nature of each interaction into the definition of the free energy of a solution. As a result, highly predictive thermodynamic models able to predict the lattice parameter of a primary phase, local lattice distortions, stored elastic energy, thermal expansion, surface energies as well as electronic and optic properties will be integrated in complex approaches used to predict the microstructural evolution of metallic materials. This will open new opportunities for scientists and engineers to design new highly performant metallic materials.