Bulk Metallic Glasses XX: Physical and Mechanical Properties II
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

Thursday 8:30 AM
March 23, 2023
Room: Aqua C
Location: Hilton

Session Chair: Eun Soo Park, Seoul National University


8:30 AM  
The Strain Rate Sensitivity of Heterogeneous Thin Film Metallic Glasses: Interplay between Nanoscale Heterogeneity and Dynamic Plasticity: Yucong Gu1; Xiao Han1; Feng Yan1; Lin Li1; 1University of Alabama
    The dynamic mechanical properties of metallic glasses (MGs) are crucial to capturing the deformation signatures, as well as for structural and functional applications. In this work, we investigate the influence of nanoscale structural heterogeneity of MGs on dynamic plasticity, focusing on the variation in strain rate sensitivity and the transition of deformation mechanisms, using a combined experimental and simulation approach. The Cu50Zr50 thin-film MGs with different nanoscale heterogeneities are synthesized using magnetron sputtering, and a transition in strain rate sensitivity as the indentation rate increases is found in the MG films with a higher heterogeneity. The mesoscale shear transformation zone dynamics simulations reveal the underlying mechanisms of the transition stem from a change in deformation mechanisms. The observed strain rate sensitivity and the corresponding mechanisms are summarized in a deformation mechanism map to provide insights into the structure and property relationship of MGs on the nanoscale.

8:50 AM  Cancelled
Temperature Dependence of Pressure Sensitivity in a Metallic Glass Composite: Priyanka Saini1; Long Zhang2; Yakai Zhao3; Haifeng Zhang2; Upadrasta Ramamurty3; Lakshmi Ramasubramanian1; 1Indian Institute of Technology; 2Shi-changxu Innovation Center for Advanced Materials, Institute of Metal Research; 3Nanyang Technological University
    The constraint factor, C, defined as hardness, H, to the yield strength, σy, ratio, which is an indirect measure of the pressure sensitivity, in bulk metallic glasses (BMG) increases as a function of temperature but shows a decreasing trend for crystalline materials. The present study investigates the variations in C for bulk metallic glass composites (BMGCs) with both transforming and non-transforming β-Ti dendrites. Indentation and uniaxial compression tests were performed to measure the H and σy, respectively, at room temperatures and elevated temperatures. High-resolution scanning electron microscopy (SEM) was used for investigating the sub-surface deformation of the BMGCs around the indent and on the side surface of compression samples. The C variations are critically assessed in terms of the interplay between shear band formation in the matrix and dislocation slip/martensitic transformation in dendrites. Finally, the implications of the results, with respect to processing of BMGCs, are discussed in detail.

9:10 AM  Cancelled
Pressure-induced Local Structural Crossover in a High-entropy Metallic Glass: Xin Zhang1; Qiaoshi Zeng1; 1Center for High Pressure Science & Technology Advanced Research (HPSTAR)
    High-entropy metallic glasses (HEMGs), as an emerging type of metallic glasses (MGs) based on the high-entropy effect, are expected to have more disordered and frustrated chemical short-range structure compared with conventional MGs. In this work, we employ pressure to monitor the atomic structural evolution of a senary HEMG, Ti16.7Zr16.7Hf16.7Cu16.7Ni16.7Be16.7, up to ∼40 GPa using in situ synchrotron x-ray diffraction. Analysis of its structure in reciprocal space in real space both reveal a pressure-induced structural crossover at ∼20 GPa with a dramatic change in short-range order (SRO), while no similar phenomenon is observed in a conventional MG, Cu36Zr64, as a control sample, suggesting the pressure-induced highly tunable SRO in HEMGs originates from the local chemical complexity, namely, the high-entropy effect. These results confirm that enhanced flexibility and tunability of atomic structures could be achieved by introducing the high-entropy effect into MGs. Configurational entropy could be another dimension for exploring MGs.

9:30 AM  
Origin of Super Plastic Behavior of Bulk Metallic Glass with Complex Icosahedral Order: Geun Hee Yoo1; Wook Ha Ryu1; Myeong Jun Lee1; Eun Soo Park1; 1Seoul National University
     Bulk metallic glasses have limited plasticity even under compression, resulting from shear localization and work softening. However, like ductile crystalline alloys, several monolithic BMGs have shown extraordinary plasticity under compression without catastrophic failure (super plastic behavior). This super plastic behavior of metallic glass is often considered because of high Poisson ratio.In the present study, we made bulk metallic glass with complex icosahedral order by adding BCC high-entropy alloy (Ti-Mo-Nb-Ta) in Zr-Cu-Ni-Al alloys. The developed metallic glass shows super plastic behavior and high fracture toughness despite the low Poisson ratio. We will report the effect of degree of icosahedral order on mechanical properties of metallic glass by systemically controlling BCC high entropy alloy contents through synchrotron high energy X-ray scattering. Through these attempts, we can figure out the role of icosahedral ordering in metallic glass and suggest an effective strategy for maximizing mechanical stability represented as super plastic behavior.

9:50 AM  
Investigation of Non-isothermal Crystallization and Mechanical Properties of Zr-based Metallic Glass with Enhanced Icosahedral Ordering: Myeong Jun Lee1; Geun Hee Yoo1; Min Kyung Kwak1; Wook Ha Ryu1; Eun Soo Park1; 1Seoul National University
    Limited plasticity in room temperature has been the obstacle for engineering application of metallic glasses. One way to overcome this problem is introduction of icosahedral medium-range order. In our past study, we have shown that substitution of Cu to TiNbTaMo high entropy alloy with optimum amount can enhance plasticity of Zr-Cu-Ni-Al metallic glass. Such composition is expected to have enhanced icosahedral cluster, which may act as effective nucleation site. In the present study, utilizing Flash DSC, we investigated the effect of icosahedral cluster on crystallization behavior of Zr-Cu-Al-Ni metallic glass by experimentally establishing CHT diagram in a wide temperature/time range. Then, by conducting nanoindentation experiment, we studied the effect of icosahedral cluster on mechanical properties of metallic glass. We expect that our study provides some insight in studying the role of icosahedral ordering in metallic glass and method of controlling its degree.

10:10 AM Break

10:30 AM  
Mechanical Properties and Scaling Laws of Bicontinuous Nanoporous Metallic Glasses: Chang Liu1; Suyue Yuan1; Jinwoo Im1; Felipe de Barros1; Sami Masri1; Paulo Branicio1; 1University of Southern California
    The mechanical properties of bicontinuous nanoporous CuxZr1-x metallic glasses (MGs) with five different compositions, x = 0.28, 0.36, 0.5, 0.64, and 0.72, and porosity in the range 0.1 < φ < 0.7 are evaluated performing tensile loading molecular dynamics simulations. Results indicate a strong dependence of the Young’s modulus (E) and ultimate tensile strength (UTS) on porosity and composition. By increasing the porosity from φ = 0.1 to φ = 0.7, the topology of the nanoporous samples shifts from closed cell to open-cell bicontinuous, inducing a brittle-to-ductile transition in the deformation and failure mechanisms, from a single critical shear band to necking and rupture of ligaments. Genetic programming (GP) is employed to uncover scaling laws for E and UTS as a function of porosity and composition, enabling accurate prediction of both the values of E and UTS in the whole range of porosity and compositions considered.

10:50 AM  
Spectroscopic Evaluation of Tribologically-induced Structural Transformations and Chemical Changes in Zr-based Bulk Metallic Glass: Hsu-Ming Lien1; Michael Chandross2; Joshua Arrington3; Filippo Mangolini1; 1University of Texas at Austin; 2Sandia National Laboratories; 3Clemson University
    Bulk metallic glasses (BMGs) are promising structural materials owing to their high elastic limit and high yield strength-to-weight ratio. Despite the attractive tribological properties (e.g., high wear resistance) of BMGs, the scientific basis for this behavior is not yet established. Notably, our understanding of shear-induced changes in the structure and surface chemistry of BMGs is still elusive. Here, we combined extended X-ray absorption fine structure (EXAFS) spectroscopic measurements with simulations of EXAFS spectra (through molecular dynamic simulations and FEFF9 calculations) to investigate tribologically-induced variations of the short-range structure of a class of BMG, namely CuZr-based BMGs. Additionally, the evolution of the surface chemistry of these BMGs was evaluated by X-ray photoemission spectroscopy (XPS). The results, shedding light on the occurrence of both shear-induced changes in the short-range structure and surface chemistry of BMGs, add significantly to our understanding of the tribological behavior of Zr-BMG in general.

11:10 AM  
Genetic Algorithm-assisted Discovery and Characterization of New Metallic Glass Coatings For Extreme Conditions: Jerry Howard1; Leslie Mushongera1; Dev Chidambaram1; Krista Carlson1; 1University of Nevada, Reno
    Metallic glasses (MGs) are an emerging class of materials possessing high corrosion and wear resistance and ease of fabrication when compared to their crystalline counterparts. However, most previously studied MGs are not useful in high-temperature environments because they undergo the glass transition phenomenon and crystallize below the melting point. In this study, GenMG – an in-house developed genetic algorithm-based tool for the discovery of novel MGs with the desired properties – was used to locate regions of high glass forming ability (GFA) and high-temperature stability in several W-based MG systems. Powders of the predicted optimal MGs were then produced via gas atomization, and the GFA of each composition was measured. MG coatings were then produced via the cold spray method. The corrosion and wear resistance of the coatings were characterized via electrochemical and tribological testing. The measured physiochemical and thermodynamic properties were used to improve future predictions made by GenMG.

11:30 AM  
Metallic Glass Coating for Improving Dicing Performance of Hard/Brittle Materials: Jinn Chu1; 1National Taiwan University of Science and Technology
    Metallic glass (MG) coatings have been shown to have many unique properties, such as high strength and low friction. The low friction characteristics of MG coatings make them potentially useful for many applications, including needles. Previously, we demonstrated MG coatings can reduce insertion/retraction resistance when the needle is punctured into a rubber. In this presentation, we extended our application to the diamond blade for dicing hard and brittle materials commonly used in semiconductors and optoelectronics. The low friction of MG-coated dicing blades was shown to effectively reduce the number and size of chips, regardless of the target substrate. Overall, SiC and sapphire were most affected by chipping, due to the fact that higher cutting forces were needed for the higher hardness of SiC and sapphire. Compared to the uncoated blade, the MG coating provided the following reductions in chipping area: Si (~23%), SiC (~36%), and sapphire (~45%).