NOMATEN HYBRID-SEMINAR January 8: On the glass transition of metallic glasses studied via fast scanning calorimetry
In-person: NOMATEN seminar room
NOMATEN HYBRID-SEMINAR
online: https://meet.goto.com/NCBJmeetings/nomaten-seminar
In-person: NOMATEN seminar room
Tuesday, JANUARY 8th 2025 13:00 CET
On the glass transition of metallic glasses studied via fast scanning calorimetry
Prof. Isabella Gallino
Technical University Berlin, Berlin, Germany
Abstract:
Only recently, the development of fast differential scanning calorimetry (or chip-calorimetry) has allowed us to characterize in situ the glass transition response of metallic glasses during cooling from the liquid over a wider range of time scales employing scanning rates from 100 K/s up to 50,000 K/s. The generally accepted description is that the vitrification kinetics should exhibit the same temperature dependence as the relaxation time for the alpha-process. However, we have recently observed that vitrification at deep undercooling may occur with a milder temperature dependence than the alpha-relaxation. The slower the system is cooled the more pronounced is the decoupling between these vitrification kinetics and the atomic mobility. As a consequence, vitrification can occur at fictive temperatures lower than those which would be obtained only accounting for the alpha-process. This apparent decoupling of the time scales for the vitrification kinetics from the time scales for the alpha-relaxation process is more pronounced at deep undercooling and for small sample sizes. This is of most importance because, it advocates a heterogeneity of cooperative atomic rearrangements, where faster mechanisms for atomic mobility that apparently are not contributing to the alpha-relaxation process, are maintaining the undercooled liquid system in (metastable) equilibrium and delay vitrification to lower temperatures.
[1] V. Di Lisio, I. Gallino, S. S. Riegler, M. Frey, N. Neuber, G. Kumar, J. Schroers, R. Busch, D. Cangialosi, Size-dependent vitrification in metallic glasses, Nature Commun. 14 (2023) 4698.
[2] X. Monnier, D. Cangialosi, B. Ruta, R. Busch, I. Gallino, Vitrification decoupling from α-relaxation in a metallic glass, Science Advances 6, eaay1454 (2020).
Bio:
Isabella Gallino was educated in Italy and in the USA. She received a degree in Chemistry from the University of Turin and a Ph.D. degree in Materials Science and Engineering from the Mechanical Engineering department of the Oregon State University. In 2005, she moved to Saarland University in Germany as a Group Leader and pursued her Habilitation in the field of Metallic Glasses.
In January 2024, she joined the Technical University of Berlin as Full Professor leading the Chair of Metallic Materials and the Research Center of Extrusion.
Her research interests are in the field of physical metallurgy and include both fundamental science and technical aspects, such as the thermophysical properties of bulk metallic glass-forming liquids and the development of innovative metal processing techniques and the discovery of new alloy compositions for commercial applications.
She is also the Chair of the Metals Staging Group of the Materials Research Society (MRS) and Editor of Materials Research Letters.
