Bulk Metallic Glasses XX: Atomic Structure
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
Tuesday 2:30 PM
March 21, 2023
Room: Aqua C
Location: Hilton
Session Chair: Amlan Das, Cornell University
2:30 PM Invited
Crystal Nucleation from a Hard-sphere Liquid: Frans Spaepen1; Zizhao Wang1; David Weitz1; 1Harvard University
The rate of crystal nucleation from the melt is one of the defining limits of glass formation. The hard-sphere system has been extensively studied theoretically, by computer simulation, and experimentally in colloidal systems. Although colloidal glasses can be readily formed, our understanding of the crystal nucleation kinetics remains incomplete. This talk will review three aspects: (i) The predictions of classical nucleation theory, based on the equations of state of the crystalline and liquid phases, and the values of the crystal-liquid interfacial free energy obtained from simulation or experiment; (ii) the predictions of full-fledged computer simulations of the nucleation events; and (iii) the experimental observations of nucleation in hard-sphere colloidal liquids. The latter will include a new technique, in which large numbers of nucleation events are observed during continuous densification of the system by sedimentation.
2:50 PM Cancelled
Ordering and Intermittent Structural Relaxation in a Model Binary Solid System: Zengquan Wang1; Peter Derlet2; Robert Maass3; 1Federal Institute of Materials Research and Testing (BAM); 2Paul Scherrer Institut; 3Federal Institute of Materials Research and Testing (BAM), University of Illinois at Urbana-Champaign
A model Lenard-Jones binary system is explored by molecular dynamics (MD) simulations up to the microsecond scale to study the isothermal structural evolution at various temperatures, around and above the glass transition temperature. The 2D and 3D diffraction patterns and their corresponding two-time correlation functions are obtained to reveal the intermittent relaxation behavior, simulating the X-ray Photon Correlation Spectroscopy (XPCS) technique. Laves C15 crystallites are nucleated and growing with time at higher temperatures, contributing to the intermittent relaxation features. Icosahedral and Frank-Kasper fragments are identified at lower temperature isotherms, leading to the structural frustration and vitrification of the system. We discuss our findings in terms of the temporal and spatially heterogeneous structural activity that underlies the simulated XPCS data and further demonstrate differences in q-space sampling.
3:10 PM
Two-step Annealing Induced Structural Rejuvenation: A Cause for Memory Effect in Metallic Glasses: Xiaodong Wang1; 1Zhejiang University
The structural origin of the memory effect is still elusive in glassy materials. In this letter, the memory effect in a series of metallic glasses (MGs) is observed by two step annealing using differential scanning calorimetry (DSC) and molecular dynamics simulations. It demonstrates that the Kovacs peak can be reflected from not only the system potential energy but also the atomic dynamics, showing the memory effect could originate from the formation of more loose packing configurations around mobile atoms by structural rejuvenation in the second step of high temperature annealing. In contrast, the high-low temperature annealing protocol can only induce the monotonic relaxation. Therefore, our results pave a pathway to better understand the origin of memory effect in MGs and other glassy materials from their dynamics and local atomic structure.
3:30 PM Invited
Enhanced Stability of Metallic Glass Thin Films using an Ion Beam at Room Temperature: Vrishank Jambur1; Chengrong Cao1; Carter Francis1; John Perepezko1; Izabela Szlufarska1; Paul Voyles1; 1University of Wisconsin
Metallic glass thin films offer better thermal stability in the form of a higher glass transition temperature, Tg, and higher hardness than the same alloy quenched from the liquid. The enhanced stability of films is likely to arise from high surface diffusivity during deposition, since the surface diffusivity of metallic glasses can be orders of magnitude higher than the bulk diffusivity. High surface diffusivity allows surface atoms to explore many configurations before being covered by additional atoms arriving from the vapor. We have demonstrated that a low energy (120-170 eV) Ar ion beam applied to the surface of metallic glass films growing at room temperature also increases stability. Films with the ion beam showed higher Tg and modestly enhanced hardness compared to films deposited at the same temperature without the ion beam. Preliminary results suggest that the same ion beam treatment dramatically increases surface diffusion at room temperature.
3:50 PM Break
4:10 PM
Ultrastable States in Bulk Metallic Glasses: Weihua Zhou1; Yi Li1; A. Lindsay Greer2; 1Institute of Metal Research, Chinese Academy of Sciences; 2University of Cambridge
There is much interest in ultrastable organic glasses obtained by thin-film deposition onto substrates of optimized temperature [1]. In this work, we explore two questions: can ultrastable states be obtained in metallic glasses? and can these states be obtained in bulk glasses (i.e. not just in deposited thin films)? We explore how the low-energy states in bulk metallic glasses can be compared with other low-energy glassy states, for example in vapour-deposited organics and in amber aged for tens of millions of years under ambient conditions. Comparing the glass-transition temperature on heating the glass (Tg) to its fictive temperature (Tf), through the parameter (Tg ‒Tf)/Tg, allows quantification of this comparison. We show that bulk-metallic-glass samples subjected to optimized mechanical treatments can achieve outstandingly stable (i.e. low-energy) states.[1] M. D. Ediger, J. Chem. Phys. 147 (2017) 210901.
4:30 PM
Correlating Rejuvenation within the Elastic Limit with Anelasticity in Metallic Glasses: Miguel B. Costa1; Alan Greer1; 1University of Cambridge
Structural rejuvenation has received much attention in the field of metallic glasses, mainly due to its potential for improvements of the fracture toughness and plasticity associated with higher-energy states. Processes within the elastic limit offer several advantages over severe plastic deformation processes, especially from a practical-application perspective. However, recent experimental evidence shows that the stored energy increases associated with these processes decay relatively fast, limiting their usefulness and hindering the efforts to understand the structural mechanisms which lead to rejuvenation. In this work, we investigate the correlation between the rejuvenation observed in processes such as elastostatic loading and cryogenic thermal cycling and anelastic (or anelastic-like) behaviours in MGs. Our results provide clues to understanding the underlying mechanisms of rejuvenation associated with elastic strains, and insights into the intricate relaxation spectra of metallic glasses with different thermal history.
4:50 PM
Structural Dynamics in the Microplastic Regime of a Zr-based Metallic Glass: Amlan Das1; Birte Riechers2; Peter Derlet3; Eric Dufresne4; Robert Maaß5; 1Cornell High Energy Synchrotron Source, Cornell University; 2Federal Institute of Materials Research And Testing (BAM); 3Condensed Matter Theory Group, Paul Scherrer Institute; 4Advanced Photon Source, Argonne National Laboratory; 5Federal Institute of Materials Research and Testing (BAM), University of Illinois at Urbana-Champaign
Nominally elastic stresses below yield can cause plastic structural activity without shear banding in a metallic glass (MG). This phenomenon in termed microplasticity and it holds significant promise in altering the structure and therefore properties of MGs. How fundamentally the structure evolves during elastic loading, remains unclear, but we could recently demonstrate both intermittent structural dynamics and increasing relaxation times with increasing stress using in-situ x-ray photon correlation spectroscopy (XPCS, Nature Communications 10, 5009 (2021)). However, these efforts focused on the long-time signature of the microplastic structural dynamics. Here we close this time-scales gap and focus on the very early structural response of a MG during elastic loading. We present the structural activity in a prototypical Zr-based MG prior to, during and immediately after application of a wide range of stresses. The results indicate strong signatures of structural activity even at the lowest possible stress levels we can apply.
5:10 PM
Across the Field of Bulk Metallic Glass - The Second Amorphous Phase: Sydney Corona1; Jong Na2; Qi An3; Yidi Shen3; William Goddard1; Konrad Samwer4; William Johnson1; 1California Institute of Technology; 2Glassimetal Technologies; 3University of Nevada, Reno; 4University of Göttingen
Across computation and experiment, multiple Bulk Metallic Glass alloy systems provide evidence of a second amorphous phase. The evidence ranges from thermodynamics, where the secondary glass provides a resolution to the Kauzmann paradox, to mechanics, composition, structure, and more. This talk compiles and summarize these results thus far, and proposes connections to existing work not previously understood as representing the secondary amorphous phase.