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Professor of Materials Science

MA University of Cambridge
PhD University of Cambridge

Microstructural Kinetics

My interest is in how materials change their structures. Understanding the mechanisms of these transformations is relevant not only for assessing the stability of materials, but also for developing new microstructures, properties and functionalities.

Metallic glasses

One route to new structures is to move further from equilibrium, and metallic glasses are a good example. Now that metallic glasses are available with minimum sections of the order of 1 cm, there is much interest in their mechanical properties, notably their exceptionally high strength, elastic strain and elastic energy-storage capacity. We focus on the mechanisms of plastic flow under ambient conditions, and on microstructural changes (see figure).

Phase nucleation

Nucleation is the first step in phase transformations. Deliberate promotion of nucleation, whether in industrial processing such as metal casting, or the control of ice formation by living systems, remains imperfectly understood, but our work shows that the nucleation kinetics can be quantitatively predicted.

Chalcogenides for data storage

Chalcogenide alloys can be reversibly switched between glassy and crystalline states. This switching can be exploited in data storage (for example in phase-change RAM), but is also of interest in areas such as neuromorphic computing. Our research, challenging because of the ultra-short switching times, focuses on crystallization kinetics.

Alloy solidification

The control of microstructure in as-cast alloys is important in optimizing their properties.  Our focus is on the use of grain refining agents to control grain size and phase dispersion, working mostly on light alloys (based on Al, Mg or Zn).

In-situ transmission electron microscopy combined with conventional and fast calorimetry to map the sequence of transformations on heating a Au-based metallic glass.

 

  • KF Kelton & AL Greer, Nucleation in Condensed Matter:  Applications in Materials and Biology, Elsevier (2010) ISBN: 978-0-08-042147-6.  (726 pp)
  • SV Ketov, YH Sun, S Nachum, Z Lu, A Checchi, AR Beraldin, HY Bai, WH Wang, DV Louzguine-Luzgin, MA Carpenter & AL Greer, “Rejuvenation of metallic glasses by non-affine thermal strain” Nature 524, 200–203 (2015).
  • H Weber, J Orava, I Kaban, J Pries & AL Greer, “Correlating ultrafast calorimetry, viscosity and structural measurements in liquid GeTe and Ge15Te85Phys. Rev. Mater. 2, 093405 (2018).
  • J Pan, YP Ivanov, WH Zhou, Y Li & AL Greer, “Strain-hardening and suppression of shear-banding in rejuvenated metallic glass” Nature 578, 559‒562 (2020).
  • YP Ivanov, CM Meylan, NT Panagiotopoulos, K Georgarakis & AL Greer, “In-situ TEM study of the crystallization sequence in a gold-based metallic glass” Acta Mater. 196, 52‒60 (2020).