Segregation at Interfaces in Lightweight Alloys towards Tailored Mechanical Properties

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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.