Abstract I

Understanding the nature of transitions between the glassy, liquid and crystalline states is a major challenge in physics as well as in materials science. With the emergence of advanced fast calorimetry, based on a chip-technology, we can nowadays access shorter and shorter time scales and thus experimentally measure the thermophysical properties of materials far from equilibrium. In this talk, we build on established and new work that our group has performed with this technique at ultra-short time scale for the study of many material characteristics. Selected topics may include: TTT-diagrams near the nose for crystallization, study of the undercooled liquid and glass formation from the melt in metallic glass-forming systems, hierarchical physical aging in bulk metallic glasses, as well as studies of the diffusion and reaction kinetics in reactive nanocrystalline multilayered thin films for more than 5 orders of magnitude of heating rates.

About the speaker

Isabella Gallino
Chair of Metallic Materials, Technische Universität Berlin (Germany)

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Abstract II

The practical strength of oxide glasses is greatly reduced by surface flaws that form during processing and use. Instrumented indentation can mimic such real-life damage events and induce flaws and cracking under controlled conditions. At the same time, instrumented indentation allows for systematic examination of the deformation and structural changes of the regions of the glass being indented. However, structural probing is nearly always performed after rather than during the sharp contact event, limiting our understanding of the indentation process. To overcome this, we here demonstrate the use of nanofocus X-ray scattering experiments to probe the local mechanical and structural response of vitreous silica during indentation. Two-dimensional mapping of the scattering pattern in the zone below a sharp diamond wedge indenter reveals local changes in the atomic structure and density as well as cracking behavior. These in situ experiments during indentation reveal the formation and evolution of the densification zone and cracking with nanoscale resolution. Understanding the interplay between structural densification and cracking behavior in glasses is deepened through this work, which is crucial for the development of more damage-resistant and thus stronger glasses as well as fundamental understanding of glass deformation mechanisms.

About the speaker

Morten Mattrup Smedskjær
Professor at Department of Chemistry and Biochemistry, Aalborg University (Denmark)

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