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

金属材料，如铝合金、镍超合金和钢，在我们的现代社会中被用于一系列高性能应用：它们被用于汽车、飞机、桥梁和发动机。根据应用的不同，它们的高比机械性能、对高温的潜在抵抗力或对高腐蚀性环境的抵抗力可能是它们比其他材料更受欢迎的几个原因之一。大多数金属和合金的高回收潜力也是选择理想材料时要考虑的一个重要方面，特别是在金属合金与复合材料竞争的航空航天和汽车工业中。******有几种加工路线来精心制作金属合金，也有许多将其转化为金属产品，如梁，螺栓，框架，轴和链轮。绝大多数金属材料在其使用寿命期间都会发生演化。有些材料会被腐蚀，其表面成分会发生变化；一些材料会经历纳米颗粒的动态沉淀并硬化；而另一些则会看到它们的体积微观结构在高温的影响下发生变化。所有这些现象的驱动力都与物质的实际状态和平衡状态之间的自由能差有关。事实上，只要平衡条件不改变，达到平衡状态的物质就不应该再进化了。因此，通常使用热处理使金属材料松弛，以确保其在使用中的稳定性。******正如这里强调的，材料的微观结构将调节其热物理性质。能够预测材料的初始微观结构及其在使用中的演变是科学家和工程师试图从数值模拟中获得的两个基本方面。所有可用的模拟材料微观结构演变的数值方法都需要一个关键因素，即对热力学驱动力的精确评估。******该研究计划旨在提供下一代金属固溶体的热力学模型，该模型将考虑所有基本的能量贡献，包括原子振动，每个原子周围的化学环境以及每个相互作用的化学性质，以定义溶液的自由能。因此，能够预测初级相晶格参数、局部晶格畸变、存储弹性能、热膨胀、表面能以及电子和光学性质的高预测性热力学模型将被集成到用于预测金属材料微观结构演变的复杂方法中。这将为科学家和工程师设计新的高性能金属材料提供新的机会。

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.