Bulk Metallic Glasses XX: 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, The Chinese Academy of Sciences; Lindsay Greer, University of Cambridge; Peter Liaw, University of Tennessee
Monday 8:30 AM
March 20, 2023
Room: Aqua C
Location: Hilton
Session Chair: Sebastian Kube, University Of Wisconsin - Madison
8:30 AM Introductory Comments
8:40 AM Invited
Studying Phase Transitions in Slow Motion via Fast Differential Scanning Calorimetry: Jörg Löffler1; 1ETH Zurich
Via applying fast differential scanning calorimetry at heating and cooling rates of several 10,000 K/s to slowly transforming bulk metallic glass (BMG)-forming systems, it is possible to explore novel glass states [1], determine their stochastics of nucleation, and study the formation of new metastable phases. Upon slow heating from low temperature, BMGs generally form metastable crystals that transform into more stable modifications at higher temperatures. However, with fast calorimetry we are able to suppress this transition and thus measure in detail the thermophysical properties of metastable phases, such as heat capacities and melting temperatures [2]. In this way, we can study phase-transition pathways [3], verify the existence of monotropic polymorphism and validate Ostwald’s phase rule for many metastable phases. [1] J.E.K. Schawe, J.F. Löffler, Nat. Commun. <B>10</B>, 1337 (2019). [2] J.E.K. Schawe, J.F. Löffler, Acta Mater. <B>226</B>, 117630 (2022). [3] S. Pogatscher et al., Nat. Commun. <B>7</B>, 11113 (2016).
9:00 AM
Uncovering the Structural Evolution of Metallic Liquids during Vitrification: Konstantinos Georgarakis1; 1Cranfield University
A metallic glass is formed when a metallic melt is cooled rapidly enough so that crystallization is avoided upon solidification. The transition of a liquid to a glass occurs with a remarkable slowdown of the dynamics in the undercooled liquid, a phenomenon which remains poorly understood. Even though viscosity increases by several orders of magnitude between the melting and the glass transition temperature, the accompanying changes in the atomic structure are rather subtle. Recent advances in levitation techniques and gave new possibilities to study liquids and undercooled metallic melts using synchrotron and neutron scattering techniques. Here we discuss the structural evolution during vitrification monitored in-situ using high-energy X-ray diffraction for a variety of glass forming liquids from above the liquidus to well below the glass transition temperature. Analysis of the changes observed in the short and medium range order contribute to the understanding of glass formation in metals.
9:20 AM
The Physics of Elemental Ag and Binary Cu-Ag Glasses: First Order Glass Transition: Qi An1; William Johnson1; Konrad Samwer1; Sydney Corona1; William Goddard1; 1Iowa State University
The glass transition is ubiquitous, while the nature of the glass state has been long been debated. Here, we examined elemental Ag and binary Cu-Ag liquids using molecular dynamics (MD) simulations from which the metastable glass state can be achieved in the simulation time scale of nanoseconds. Our MD simulations proof that the glass transition in these metallic liquids is a 1st order freezing transition from a high temperature liquid-like disordered phase (L-phase) to a heterogeneous, elastically rigid, low temperature solid-like phase (G-phase). The robust metastability of glass phase in the MD simulations enables us to apply thermodynamic principles to construct a glass-crystal-liquid phase diagram over a broad range of temperature. The L-phase and G-phase are further distinguished by the vibrational density of state, and mechanical response under shear deformation. The first order L-G transition is fundamentally linked to the emergence of long-range elasticity and elastic interactions in the glass.
9:40 AM Invited
Compositional Dependence of the Fragility in Metallic Glass Forming Liquids: Sebastian Kube1; Sungwoo Sohn1; Rodrigo Ojeda Mota1; Theo Evers1; William Polsky1; Naijia Liu1; Kevin Ryan1; Sean Rinehart1; Yong Sun1; Jan Schroers1; 1Yale University
The viscosity and its temperature dependence, the fragility, are key properties of a liquid. A low fragility is believed to promote the formation of metallic glasses. Yet, the fragility remains poorly understood, since experimental data of its compositional dependence are scarce. Here, we introduce the Film Inflation Method (FIM), which measures the fragility of metallic glass forming liquids across wide ranges of composition and glass-forming ability. We determine the fragility for 170 alloys ranging over 25 at.% in Mg-Cu-Y. Within this alloy system, large fragility variations are observed. Contrary to the general understanding, a low fragility does not correlate with high glass-forming ability here. We introduce crystallization complexity as an additional contribution, which can potentially become significant when modeling glass forming ability over many orders of magnitude.
10:00 AM Break
10:20 AM
Measurements from the Gap: Viscosity and Wave Speed Measurements in the Supercooled Liquid Region: Robert Conner1; Stefan Lohaus2; Rebecca Stevens1; Joseph Serrano1; 1California State University Northridge; 2California Institute of Technology
Deformation and flow behavior in bulk metallic glasses (BMGs) are well characterized at temperatures below the glass transition temperature and in the molten liquid by conventional methods, e.g. beam bending and rotating-cup viscometry. However, data is virtually absent in the supercooled liquid (SCL) region, due to the quick onset of crystallization limiting the time available for measurements. We developed an experimental setup, based on rapid discharge heating, to determine the viscosity and shear modulus of Pd-based and Ni-based BMGs in the SCL region. Shear moduli are determined from ultrasonic wave speeds measurements on heated samples, and the viscosity by tracking their deformation under an applied pressure. These are missing quantities for validating existing theories on the relaxation kinetics and rheology of metallic glasses in the SCL region, such as the Cooperative Shear Model. This work is supported by NSF award 1710741
10:40 AM
Thermodynamic Connections to the Fragility of Pt-based BMGs: Hillary Smith1; Colby Stoddard1; Jong Na2; Marios Demetriou2; 1Swarthmore College; 2Glassimetal
A new series of bulk metallic glasses (BMGs) Pt80-xCuxCu20 were recently reported with Angell fragility parameters ranging from 73 to more than 90 [1]. The effect of fragility on thermodynamic properties in these metal/metalloid glasses has been systematically investigated using differential scanning calorimetry. The thermodynamic functions of excess enthalpy, entropy, and Gibbs free energy between the liquid and crystal phases were calculated as a function of x (Cu concentration) from the isobaric specific heat capacity measurement of the glass, crystal and liquid. The glass transition, crystallization, and liquidus temperatures, and the enthalpies of crystallization and melting were also assessed. We will discuss the correlation between fragility and excess specific heat at the glass transition. Fractional contributions of vibrational entropy to the entropy of the glass and undercooled liquid as determined from inelastic neutron scattering will also be reported.1. Na, J.H., et al., P.N.A.S. 117, 2779 (2020).
11:00 AM
In-situ XRD Studies of Crystallization and Phase Transformations in Metallic Glasses upon Ultrafast Heating: Ivan Kaban1; 1IFW Dresden
Knowledge of the thermal stability of metallic glasses and formation of crystalline phases upon ultrafast heating is of high importance for practical applications. For example, to avoid crystallization by fabrication of metallic-glass parts or to design metallic-glass/crystal composites with desired phase(s). In this talk, results of recent in-situ studies of metallic glasses upon heating at a rate between about 10^2 and 10^5 K/s using high-energy X-ray diffraction and scattering at German Electron Synchrotron DESY, Hamburg will be presented and discussed.
11:20 AM
Imaging Crystallization of a Au-based Bulk Metallic Glass: Influence of the Initial Glassy State: Owain Houghton1; A. Greer1; Yurii Ivanov1; 1University of Cambridge
On heating, a bulk metallic glass (BMG) first enters the supercooled-liquid region, and then crystallizes. Conventionally, the state of the BMG is considered irrelevant for crystallization; the supercooled liquid has no 'memory' of the initial glass. The Au49Pd2.3Ag5.5Cu26.9Si16.3 BMG chosen for the present work has been very widely studied, not least because this composition can be melted and revitrified in fast differential scanning calorimetry (FDSC) - this allows characterization immediately after glass formation. We present in-situ imaging (HRTEM and STEM) of crystallization during annealing below the glass-transition temperature to explore how changes to the glassy state (the extent of α and β relaxation and embedded crystalline nuclei) can affect the crystallization upon heating.The findings are relevant not only for metallic, but also for silicate and perhaps other, glassy systems.