Bulk Metallic Glasses XX: Structural Dynamics and Local Strains
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 8:00 AM
March 21, 2023
Room: Aqua C
Location: Hilton
Session Chair: Robert Maass, Federal Institute of Materials Research and Testing (BAM)
8:00 AM Invited
A Spatially Resolved View on Heterogeneous Dynamics in Metallic Glasses: Gerhard Wilde1; 1University of Muenster
Local dynamics of atomic rearrangements underlie the characteristic relaxation behavior of glasses. Important properties, such as yielding of metallic glasses also seem to be affected by rearrangements that represent at least a part of the relaxation spectrum. Thus, the atomic dynamics presents an important parameter for understanding and tuning the properties of (metallic) glasses. Measures for modifying the relaxation spectrum are e.g. thermal aging, plastic deformation or cryogenic rejuvenation. Understanding the interdependencies between local structural motifs and their dynamics and macroscopic properties such as long-range diffusion or calorimetric signatures as well as their dependence on macroscopic changes of the relaxational state is as yet incomplete. Selected results obtained by combining different experimental methods, i.e. fluctuation electron microscopy, electron correlation microscopy, radiotracer diffusion and calorimetry serve to discuss apparent correlations between relaxation – or rejuvenation treatments and resulting modifications of medium-range order and the time scales of heterogeneous glassy dynamics.
8:20 AM Invited
Pressure Dependence of the Collective Motion in Metallic Glasses Studied with Coherent X-rays: Beatrice Ruta1; Antoine Cornet1; 1Univ Lyon 1 and CNRS
X-ray Photon Correlation Spectroscopy (XPCS) is a spatio-temporal coherent X-ray scattering technique that probes slow collective dynamics at the nanometric and atomic scale based on the observation of fluctuating far-field speckle patterns. This technique has been successfully applied to the investigation of slow relaxation processes occurring in metallic glass-formers undergoing dynamical arrest, polyamorphism and aging, such as liquid alloys and metallic glasses. The Extreme Brilliance Source (EBS) upgrade of synchrotron ESRF has extended dramatically the dynamical range of XPCS with a considerable increase of the coherent flux at higher photon energies, making possible in-situ high pressure (HP) studies in complex systems. In this talk, I will present recent experimental results on the atomic motion in a metallic glass obtained with HP-XPCS at ESRF-EBS, and I will also illustrate some of the future scientific possibilities offered by this technique in the field of high pressure science in glass formers.
8:40 AM
Long-time Structural Evolution of Metallic Glasses: Robert Maass1; Birte Riechers2; Amlan Das3; Zengquan Wang2; Eric Dufresne4; Peter Derlet5; 1Federal Institute of Materials Research and Testing (BAM), University of Illinois at Urbana-Champaign; 2Federal Institute of Materials Research and Testing (BAM); 3Cornell High Energy Synchrotron Source; 4Advanced Photon Source, Argonne National Laboratory; 5Condensed Matter Theory Group, Paul Scherrer Institut
Structural relaxation is often considered to be a continuous process characterized by steadily increasing relaxation times. However, recent literature shows distinct intermittent aging events. Here, we shed light onto long-time aging signatures of a Zr-based bulk metallic glass at 0.98Tg using x-ray photon correlation spectroscopy (XPCS). Probed over the duration of eight individual experiments of ca. 35000 s each, we reveal temporal fluctuations of all extracted quantities, including the short-time plateau, the first moment in time, the relaxation time, and the shape parameter. Whilst strong fluctuations of any investigated parameter may appear as a rare event in an individual two-time correlation function, variations over larger timescales emerge as the norm, which emphasizes the time-scale interplay between an experimental time and a broad distribution of material timescales. This suggests that aging close to or below Tg is generally a temporally heterogeneous process, if sufficiently sampled in time.
9:00 AM Cancelled
Low-temperature Relaxation and Crystallization Processes in Metallic Glasses: Dmitri Louzguine1; 1WPI-AIMR, Tohoku University
Relaxation and crystallization processes in metallic glasses below the glass-transition temperature are examined by using differential scanning calorimetry, X-ray diffractometry and transmission electron microscopy. Although densification of a Cu36Zr48Al8Ag8 bulk metallic glass takes place owing to beginning of structural relaxation both mechanical strength and plasticity values are increased [1]. However, no clear structural changes in terms of crystallization or phase separation are observed. The results are partly interpreted in terms of release of internal stresses. Also, a combination of solute partitioning and isothermal linear growth which challenges usual assumptions about the characteristics of primary and polymorphic crystallization was found in a Mg-Ni-Mm alloy [2]. This hybrid behavior is interpreted in terms of different diffusivities of the atomic species in this system. 1. D. V. Louzguine-Luzgin and J. Jiang, Mater. Sci. and Eng. A, 839, (2022), 142841.2. Yu.P. Ivanov, et al., J. Alloys and Comp., 909, (2022), 164732.
9:20 AM
Origin of α-relaxation in Metallic Liquids: Chae Woo Ryu1; Takeshi Egami1; 1University of Tennessee
The α-relaxation time determined by scattering experiments and simulation as the decay rate of the first peak of the structure function, S(Q), τ(Qmax), is commonly interpreted as the structural relaxation time which represents the collective atomic dynamics, but we usually overlook its origin. Here we investigate the origin of the α-relaxation time through the examination of the Van Hove correlation function in real space. We show that the α-relaxation time reflects all dynamics from the short-rang order (SRO) and the medium-range order (MRO), although the disparate natures of the SRO and the MRO are clearly seen in the dynamic correlations of atoms. This investigation leads to more rigorous interpretation of the α-relaxation time determined by scattering experiments.
9:40 AM Break
10:00 AM Invited
Non-affine Strains in Glassy Solids: Wojciech Dmowski1; Chae Woo Ryu1; Hui Wang1; Takeshi Egami1; 1University of Tennessee
In simple crystals, at low temperatures, the elastic response can be calculated from affine deformation of the lattice by rescaling of lattice parameters. In disordered materials every atom has a distinctive atomic environment and thus the response of every atom to the macroscopic stress can be different resulting in non-affine displacements of the atoms. Being a natural consequence of the disorder of microscopic interactions the non-affine displacement field is responsible, in particular, for the breakdown of Born-Huang’s formulation of elastic moduli. The heterogeneity of elastic deformation has been experimentally demonstrated for metallic glasses. In covalent systems the bond rotation can play crucial role in accommodating the deformation. We examined the response of the atomic structure to the stress of metallic, oxide and polymeric glasses elucidating the r-dependence and length-scale of non-affine strains, using x-ray scattering.Supported by the U.S. Department of Energy, Basic Energy Sciences, Materials Science and Engineering Division.
10:20 AM
Stress-strain Measurements on Cyclically Sheared Colloidal Glasses: J. Zsolt Terdik1; David Weitz1; Frans Spaepen1; 1Harvard University
Measuring the stress response of colloidal glasses, simultaneously with confocal visualization, presents a significant challenge. The micron size of the particles and thermal interaction energies result in exceptionally small elastic moduli, on the order to ~1Pa. We introduce a new technique, traction rheoscopy, in which a colloidal glass is deposited on a soft polymer gel with a calibrated shear modulus. This composite bilayer is sheared, and the shear stress is determined from the displacement of embedded tracer particles in the gel. We show that, as the stress develops, the colloidal glass goes through as sequence of reversible and irreversible microscopic rearrangements that result in spatial strain heterogeneities. We corroborate previously reported microscopic flow mechanisms and present new insight into the response of colloidal glass to shear. Our latest results are on a colloidal glass subjected to a series of cyclic strains, with maxima increasing from ~0.1% to 15%.
10:40 AM
Local Strain Analysis by 4D-STEM on Zr50Cu40Al10 Subjected to High Pressure Torsion: Katsuaki Nakazawa1; Sangmin Lee1; Kazutaka Mitsuishi1; Shinji Kohara1; Koichi Tsuchiya1; 1National Institute for Materials Science
Although bulk metallic glasses (BMG) have superior properties to crystalline metals such as high strength and high corrosion resistance, shear localization during straining limits the area of application of BMGs. Structural rejuvenation by high pressure torsion (HPT) can suppress the shear band formation and may lead to improved plastic deformability. However, details of the local atomic structure in rejuvenated BMG have not been clarified yet.We used 4D-STEM to characterize a change in local atomic structures caused by HPT in Zr50Cu40Al10 BMG. The local strain was measured from the diffraction patterns obtained by a convergent electron beam. We obtained a localized strain map by scanning the convergent electron beam and recording diffractions from all the scanning points. It was revealed that HPT induced anisotropic strain in BMG.
11:00 AM
Structural Symmetry of Medium Range Ordering in Metallic Glasses Revealed by Angular Correlation Analysis of 4D-STEM Nanodiffraction: Gabriel Calderon1; Jiyoung Kim2; Geun-Hee Yoo2; Chaoyi Liu3; Soohyun Im4; Minhazul Islam1; Yue Fan3; Eun Soo Park2; Jinwoo Hwang1; 1Ohio State University; 2Seoul National University; 3University of Michigan; 4University of Wisconsin Madison
Angular correlation (AC) analysis of 4D-STEM nanodiffraction was used to determine the type and degree of medium range ordering (MRO) that constitutes the nanoscale heterogeneity in Zr-Cu and Zr-Cu-Al metallic glasses (MGs). AC reveals significant changes in MRO as the composition changes, such as from binary to ternary, as well as from eutectic to hypereutectic. The changes include the splitting of 2-fold peaks (which indicates the separation of MRO types) in more fragile glasses, and the emergence of strong 6-fold symmetries in more strong glasses. We correlate these results to the changes in fragility, ductility, and glass forming ability of these glasses. ACs from atomistic models were also simulated and compared to the experimental ACs from the same composition, which is a necessary effort to advance toward developing new atomistic models that generate fully realistic MRO structures.