Bulk Metallic Glasses XIX: 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, Chinese Academy of Sciences; Lindsay Greer, University of Cambridge; Peter Liaw, University of Tennessee
Wednesday 8:30 AM
March 2, 2022
Room: 253C
Location: Anaheim Convention Center
Session Chair: Alex Dommann, Empa
8:30 AM
Investigating the Structural Origin of the Change in Ductility of Zr-Cu-Co-Al Metallic Glasses Using 4-dimensional Scanning Transmission Electron Microscopy: Soohyun Im; Pengyang Zhao1; Yuchi Wang2; Geun Hee Yoo3; Eun Soo Park3; Yunzhi Wang2; Jinwoo Hwang2; 1Shanghai Jiao Tong University; 2The Ohio State University; 3Seoul National University
The atomic structure of metallic glasses (MGs) may be inherently connected to the way shear transformation zones activate, but the details of such connection remain unclear. We investigate the medium-range ordering (MRO) and structural heterogeneity in Zr-Cu-Co-Al MGs that may directly correlate with the significant increase in ductility observed in that system. Angular correlation analysis and digital real-space reconstruction of the nanodiffraction acquired using 4-dimensional scanning transmission electron microscopy revealed that types of the MRO vary in 3 compositions, Zr45Cu50Al5, Zr55Co25Al20, and the mixture of the two, Zr50Cu25Co12.5Al12.5, with some of the MRO resembling the structural symmetry of stable intermetallic phases. Importantly, Zr50Cu25Co12.5Al12.5 shows smaller and more frustrated MRO structure, which may correlate with the substantially increased ductility in this composition. The result highlights why some MGs are intrinsically more ductile than others, which may provide important implications to designing the nanoscale structure to optimize the MGs’ properties.
8:50 AM Invited
Determining the Three-dimensional Atomic Structure of Metallic Glass: Jianwei Miao1; 1Univ of California Los Angeles
Using a multi-component metallic glass as a model, we advanced atomic electron tomography to determine its 3D atomic positions and chemical species with a precision of 21 picometer. We quantified the short-range order (SRO) and medium-range order (MRO) of the 3D atomic arrangement. We observed that some SRO structures connect with each other to form crystal-like networks and give rise to MRO. We identified four types of MRO - face-centred cubic, hexagonal close-packed, body-centered cubic and simple cubic - coexisting in the sample, showing translational but not orientational order. We quantified the size, shape, volume, and structural distortion of MRO with unprecedented detail. Looking forward, we anticipate this experiment will open the door to determining the 3D atomic coordinates of various amorphous solids, whose impact on non-crystalline solids may be comparable to the first 3D crystal structure solved by x-ray crystallography over a century ago.
9:15 AM
Structural Origin of Ultrastable Metallic Glasses: Zhen Lu1; Akihiko Hirata2; Mingwei Chen3; 1WPI-AIMR, Tohoku University; 2Waseda University; 3Johns Hopkins University
Ultra-stable metallic glasses, fabricated by high-temperature physical vapor deposition, possess superior thermodynamic and kinetic stability. However, the structural origins of the unique glass state have not been well explored. Here we report that the outstanding thermodynamic and kinetic stability of an ultra-stable ZrCu metallic glass originates from ubiquitous crystal-like medium range order with well-defined local translational symmetry beyond nearest neighbors. The crystal-like order significantly improves the kinetic stability of the glass and the thermodynamic stability of its supercooled liquid, which is in opposition to the conventional wisdom that crystal-like order deteriorates the stability and forming ability of glasses. This study unveils the structural origin of ultrastable metallic glasses and shines insights into the intrinsic correlation of local atomic order with kinetic properties and glass transition of metallic glasses.
9:35 AM
X-ray Techniques to Study the Interplay of Short- and Long-range Structural Ordering in Zr and Pd Bulk Metallic Glasses: Alex Dommann1; Aurelio Borzi1; Antonia Neels1; 1Empa
We will discuss the potential of different X-Ray techniques helping to develop a deeper understanding of the unconventional modality of deformation through highly localized shear bands, resulting in macroscopic brittleness which leads to catastrophic failure. The solidification of Zr- and Pd- based BMGs under gravity and micro-gravity conditions [1] has been studied by means of different X-ray techniques like diffraction and total scattering after processing. We obtained results on atomic pair-pair correlation functions that are about the local structure of the system, which allowed us to estimate the bond length, the average coordination number, and the free volume, a parameter that corre-lates the structure and properties of BMGs, such as the glass-forming ability and me-chanical properties. [1] M. Mohr, R. Wunderlich, K. Zweiacker, S. Prades-Rödel, R. Sauget, A. Blatter, R. Logé, A. Dommann, A. Neels, W. Johnson, H. Fecht, NPJ Microgravity, 2019, 5(1), 4, 1-8, (2019).
9:55 AM Discussion on atomic structure of metallic glasses