Advancing microstructure modeling of rapid thermomechanical processes: Experiment-modelling synergy using a novel CW Laser and SEM coupling (10/02/25)
Speaker and Affliation:
Prof. Manas V. Upadhyay
Department of Mechanics of the Ecole Polytechnique, France.
When?
10th February, 2025 (Monday), 04.00 PM (India Standard Time)
Where
KPA Auditorium, Dept. of Materials Engineering, IISc, Bangalore
Abstract:
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; until recently, simulation predictions were being unfairly compared against vastly more complex results from AM experiments.
To remedy this problem, a novel coupling between a continuous-wave laser and a scanning electron microscope (CWLaser-SEM) was recently developed [1–4]. One of the biggest advantages 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 laser scanning at the same locations without any mechanical polishing in between measurements. This generates a clean set of experimental data that not only serves as input for the models but also allows performing a one-to-one comparison with their predictions.
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 [4], as well as a thermo-elasto-viscoplastic finite element model to predict formation of residual intergranular stresses and plastic strains [3] 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 aforementioned CWLaser-SEM device can be used to generate thermomechanical conditions that not only mimic AM processes but also other thermomechanical processes such as welding and quenching, and thus be useful to validate a host of different models. Furthermore, this device have 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
About the Speaker:
Manas V. Upadhyay is a Professor in the Department of Mechanics of the Ecole Polytechnique (France), and the Program Director of Masters of Mechanics at the Institut Polytechnique de Paris, a conglomerate of 6 “Grandes Ecoles” in France. He obtained his PhD from the Georgia Institute of Technology (USA) in 2014 and he did his post-doctoral research from 2014 – 2018 at the Paul Scherrer Institute (Switzerland). He joined the Ecole Polytechnique in January 2019 as an Assistant Professor. He obtained his HDR (Habilitation to Direct Research) diploma in October 2022 and was promoted to Professor in September 2024.
His general research interest is in Extreme Thermomechanics and Materials Engineering. His current research can be broadly classified into two themes: (i) Engineering metal microstructures for tailored mechanical properties and (ii) Modelling extreme micro-thermomechanics. In the past 6 years, he has worked extensively on the topic of microstructure engineering and micro-thermomechanical modelling of additive manufactured alloys. He has received multiple research grants for his work, notably the prestigious European Union’s Horizon2020 ERC Starting Grant 2020 (946959). He has also received awards for his professional activities, notably the Jean and André Rist 2022 medal by the French Society of Metallurgy and Materials (SF2M).
His research group perseveres to understand metal microstructure formation and evolution from the length-scale where individual defect dynamics can be studied to the polycrystalline level, and to harness this understanding to tailor microstructures with desired properties. What sets his group apart is that they actively develop experimental devices and conduct advanced characterization experiments (primarily SEM, TEM, and synchrotron XRD) in synergy with developing theoretical models and performing numerical simulations (primarily, crystal plasticity and dislocation dynamics). More information on his professional activities can be found at https://www.manas-upadhyay.com