Advancing microstructure modeling of rapid thermomechanical processes: Experiment-modelling synergy using a novel continuous-wave laser and SEM coupling
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The last 10 years have seen the development of multi-physics models to predict microstructure formation during rapid thermomechanical processes, particularly in the context of metal additive manufacturing (AM), in order to eventually propose solutions to design microstructures for desired properties. A critical step to achieving this aim is to validate these models by performing a fair one-to-one comparison between simulation predictions and experiments. Typically, simulation predictions have been compared against vastly more complex results from experiments resembling AM builds, while validation at the scale of individual laser tracks is much less common. To remedy this problem, a novel coupling between a continuous-wave laser and a scanning electron microscope (CWLaser-SEM) was recently developed [1–4]. An important advantage of this coupling is that it allows performing laser scanning in the secondary vacuum of the SEM, which effectively eliminates the risk of surface oxidation. Therefore, the full range of SEM measurements can be performed before and after lasering at the same locations without any intermediate mechanical polishing. This generates a clean set of experimental data that serves not only as input for models but also as a basis to validate them. The first experiments performed with the CWLaser-SEM were performed on 316L stainless steel. They were designed to validate a combined computational fluid dynamics and phase-field grain growth model for fast solidification at the polycrystalline level [3], as well as a thermo-elasto-viscoplastic finite element model to predict formation of residual intergranular stresses and plastic strains [4] due to laser scanning. The design of the CWLaser-SEM, development of the experiment-modelling synergy and results of these studies will be presented. The CWLaser-SEM device can be used to generate conditions that not only mimic AM but also other processes such as welding and quenching. Furthermore, this device has been helpful in developing post-processing routes to engineer microstructures of additive manufactured stainless steels in order to enhance their overall mechanical properties (strength, ductility and fatigue limit) [2]. References: [1] Patent pending: A. Tanguy, M. V. Upadhyay, J. G. Santos Macías, submitted: 16 Dec 2022 [2] Santos Macías et al., preprint: https://hal.science/hal-04530203 [3] Chadwick et al., Acta Materialia 282 (2025) 120482 [4] Mohanan et al., Materialia 34 (2024) 102082