Segregation at Interfaces in Lightweight Alloys towards Tailored Mechanical Properties

近年来，与能源生产和运输相关的温室气体减排和燃油效率增加了人们对轻质合金开发的兴趣。在这种趋势下，涉及回收的可持续材料变得至关重要。镁合金是实现这一目标的主要候选材料，但镁合金在环境温度下的延展性较差，使得加工和成型具有挑战性且成本高昂，阻碍了镁合金的广泛应用。了解含有所需和不需要溶质元素的合金的塑性机制是设计具有定制力学性能的轻质合金的必要步骤。SILA项目建议通过改进和发展连续统模型来应对这一挑战，该模型能够预测晶界处的溶质偏析及其对机械性能的影响，并得到实验和原子结果的支持。梅斯的LEM3是力学和晶体缺陷连续体建模的领导者，亚琛的IMM是镁合金实验表征的领导者，这是一项独特的法德合作，提议采用原子模拟来弥合原子尺度实验和连续体模型之间的差距。SILA将考虑双晶和三晶的镁与锌或Y溶质元素。原子探针层析成像的原子尺度实验表征将用于验证分离界面的分子静力学/动力学模拟。模拟的原子细节将提供基于界面自由能过剩的新型连续体模型，该模型能够捕捉界面上的化学-力学过程，包括晶界上现有缺陷之间的复杂相互作用。实验和数值纳米力学测试将探索镁合金的力学响应，包括与位错的相互作用，并描述界面上溶质偏析的作用。SILA的目的是精确的，基于实验的，连续描述晶界与分离元素，以改进应变时效合金的本构模型。这对于工程合金和再生合金至关重要，因为这些合金在界面处的分离溶质对其机械性能影响很大。

Greenhouse gas reductions and fuel efficiency associated with energy generation and transportation have led to increased interest in the development of lightweight alloys in recent years. Following this trend, sustainable materials involving recycling have become of crucial importance. Magnesium alloy is a major candidate to achieve this goal but suffers from poor ductility at ambient temperature, making the processing and forming challenging and costly and preventing widespread applications. Understanding the mechanisms of plasticity in such alloy containing desired and undesired solute elements is the necessary step towards the design of lightweight alloys with tailored mechanical properties.The project SILA proposes to contribute to this challenge by the improvement and development of continuum models able to predict solute segregation at grain boundaries and its impact on mechanical properties, supported by experimental and atomistic results. A unique French-German collaboration between the LEM3 in Metz, the leader in the continuum modelling of mechanics and crystalline defects, and the IMM in Aachen, the leader in the experimental characterization of Mg alloys, proposes to employ atomistic simulations to bridge the gap between atomic-scale experiments and continuum models.SILA will consider bi- and tri-crystals of Mg with Zn or Y solute elements. Atomic-scale experimental characterisation by atom probe tomography will be used to validate molecular statics/dynamics simulations of the segregated interfaces. The atomistic details of the simulations will feed novel continuum models based on the excess of interfacial free energy able to capture the chemo-mechanical processes at interfaces, including complex interactions between present defects at grain boundaries. Experimental and numerical nano-mechanical tests will explore the mechanical response of the Mg alloys, including the interaction with dislocations, and describe the role of solute segregation at interfaces.SILA aims at an accurate, experiment-based, continuum description of grain boundaries with segregated elements, to improve constitutive models for strain-aged alloys. This is of prime importance for engineering alloys and recycled alloys whose segregated solutes at interfaces impact largely mechanical properties.