Bulk Metallic Glasses XIX: Glass-forming Ability and the Glass Transition
Sponsored by: TMS Structural Materials Division, TMS: Mechanical Behavior of Materials Committee
Program Organizers: Robert Maass, Federal Institute of Materials Research and Testing (BAM); Peter Derlet, Paul Scherrer Institut; Katharine Flores, Washington University in St. Louis; Yonghao Sun, Chinese Academy of Sciences; Lindsay Greer, University of Cambridge; Peter Liaw, University of Tennessee

Thursday 10:00 AM
March 3, 2022
Room: 253C
Location: Anaheim Convention Center

Session Chair: Paul Voyles, University of Wisconsin

10:00 AM  Invited
Surface Mobility of Metallic Glass Thin Films Controls Glass Phase Stability and Crystallization: Debaditya Chatterjee1; Ajay Annamareddy1; Chengrong Cao1; Yuhui Li1; John Perepezko1; Lian Yu1; Dane Morgan1; Paul Voyles1; 1University of Wisconsin
    Metallic glass surfaces have much higher mobility than the interior of the glass at the same temperature in both experiments and simulations. Electron correlation microscopy experiments show that surface dynamics, like bulk dynamics, are spatially heterogeneous. Surface diffusivity and surface relaxation time slow down with cooling in a way similar to the bulk glass transition at a temperature Tg,s well below the bulk glass transition temperature Tg,b. The surface and bulk diffusivities near these temperatures scale such that Ds(Tg,s / T) = Db(Tg,b / T). High surface mobility enables physical vapor deposition of highly stable metallic glass films with increased structural order, and helps determine which combinations of deposition rate and substrate temperature result in amorphous films and which result in crystalline films. Metallic glasses fit into a general trend connecting surface mobility to bulk liquid fragility that cuts across many different types of glasses.

10:25 AM  
Inside Glass Tormation: The Pathway of Metallic Liquids to Vitrification Monitored in Situ by Ultrafast High-energy Synchrotron X-ray Diffraction: Martin Stiehler1; Mark Jolly1; Konstantinos Georgarakis1; 1Cranfield University
    Liquid metallic melts can be vitrified into glasses when cooled fast enough to avoid crystallisation. The mystery of glass formation lies in the contrast between only very subtle changes in the atomic structure and the accompanying increase of viscosity by many orders of magnitude. Additionally, further intriguing phenomena like liquid-liquid crossovers occur along the pathway to vitrification. Here we discuss structural changes in aerodynamically levitated samples of metallic-glass-forming liquids observed in situ by ultrafast high-energy X-ray diffraction from temperatures well above the liquidus temperature to below the glass-transition temperature. This enables a detailed investigation of the miniscule changes of the atomic arrangements leading to the tremendous slowdown of the kinetics during vitrification. Analysis of the short- and medium-range order indicates temperature dependent structural changes pointing to liquid-liquid crossovers. The temperature dependence of structural metrics can also help to clarify the influence of global electronic effects on glass formation.

10:45 AM  
Structural Influences on Glass Forming Ability in Mg-Ni-Y: Carter Francis1; Janine Erickson1; John Sunderland1; Chengrong Cao1; Dan Thoma1; John Perepezko1; Paul Voyles1; 1University of Wisconsin Madison
    We have used 4-dimensional scanning transmission electron microscopy to show that Mg77Ni18Y5 has significant crystal-like ordering which gives rise to 4- and 6-fold rotational symmetries in nanodiffraction and icosahedral-like ordering which gives rise to 10-fold rotational symmetries. This alloy can be cast into 1 mm diameter rods and has a critical cooling rate between 20,000 and 30,000 K/s as measured by high thermal rate calorimetry. Symmetries in nanodiffraction were determined using the recently developed symmetry coefficient method, which, combined with high dimensional clustering methods, allows us to measure the size, approximate internal interatomic spacings, rotational symmetry, and spatial distribution of individual ordered clusters in the glass.

11:05 AM Discussion on glass formation of metallic glasses