Micromechanical behavior of nanostructured oxides at Very High Temperature – Experimental investigations and virtual multiscale material design
Final Report Abstract
The oxide compounds often crystallize under low symmetry, exhibit anisotropic elastic properties and are subject to a number of solid state phase transformations (SPTs) as a function of temperature and pressure. As a result, the global thermomechanical behaviors of polycrystalline ceramic materials cannot be predicted from the fundamental properties of corresponding crystals. Such global properties are indeed related to nanoscale characteristics, typically below 100 nm, i.e. below the ceramic grain size. In essence, the objective of HoTMiX project was to gain fundamental knowledge of the interplay between plastic and elastic strains at very high temperature at this nanoscale in oxide based materials. The role of microcracking should have been elucidated for both ceramics with high anisotropy and undergoing SPT. Advanced characterization methods (synchrotron X-ray micro-tomography, X-ray refraction, diffraction, and scattering), and 3D computational models were used, all representing cutting edge science. These methods were further developed to extend its use to very high temperatures, as well as to combine in-situ loading and high temperatures. This had an impact in the scientific community of the large-scale facilities, starting from those residing at the ESRF and at BESSY II synchrotrons. From the modeling point of view, the "virtual microstructure" approach enabled the investigation of materials at temperatures even higher than experimental measurements. We expect that such an approach will have a deep impact on the scientific knowledge. The German partners offered unique competence areas (microstructure simulations from UUlm, X-ray refraction from BAM), which strongly complement the French team. Vice versa, the French consortium offered access to experimental large-scale facilities (ESRF) and simulation tools (e.g., discrete element simulations). Thanks to the frequent project meetings, a vibrant scientific exchange was fostered, which led to some technology transfer between the two countries and the build-up of a long-term collaboration. BAM activity was first focused on the development of the in-situ heating capabilities. The Anton Paar furnace at BAM was successfully integrated to the refraction BAMline setup (BESSSY II of HZB), proven to be adequate for the study of metals although insufficient for the case of refractory materials. Thus, a collaboration with Elettra synchrotron (Trieste, I) was established in order to adapt their inhouse developed induction furnace (up to 1400°C) to the BAMline. This collaboration enabled to monitor closure and opening of microcracks in Aluminium Titanate (AT) and ZrO2 as a function of temperature. The virtual zirconia microstructures generated by UUlm allowed modeling the SPT from cubic to tetragonal taking place at very high temperatures, hard to observe experimentally. In combination with the micromechanical analysis performed at PIMM, novel insights into the stress field during this SPT were obtained. UUlm also employed advanced computational methods for the characterization of materials. For instance, it was possible to accelerate the data analysis pipeline necessary for Laue microdiffraction measurements, to further illuminate the sub-grain formation in pure aluminum during creep (taken as a model material at high temperatures), as well as a to describe in a detailed statistical manner the microstructure of AT.
Publications
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Synchrotron X-ray refraction detects microstructure and porosity evolution during in-situ heat treatments. Materials Science and Engineering: A, 838, 142732.
Serrano-Munoz, Itziar; Roveda, Ilaria; Kupsch, Andreas; Müller, Bernd R. & Bruno, Giovanni
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CNN-Based Laue Spot Morphology Predictor for Reliable Crystallographic Descriptor Estimation. Materials, 16(9), 3397.
Kirstein, Tom; Petrich, Lukas; Purushottam, Raj Purohit Ravi Raj Purohit; Micha, Jean-Sébastien & Schmidt, Volker
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Statistical Comparison of Substructures in Pure Aluminum Before and After Creep Deformation, Based on EBSD Image Data. Microscopy and Microanalysis, 29(6), 1889-1900.
Rieder, Philipp; Petrich, Lukas; Serrano-Munoz, Itziar; Fernández, Ricardo; Bruno, Giovanni & Schmidt, Volker
