Bulk Metallic Glasses XVII: Mechanical and Other Properties
Sponsored by: TMS Structural Materials Division, TMS: Mechanical Behavior of Materials Committee
Program Organizers: Peter Liaw, University of Tennessee; Yanfei Gao, University of Tennessee-Knoxville; Hahn Choo, University of Tennessee; Yunfeng Shi, Rensselaer Polytechnic Institute; Robert Maass, Federal Institute of Materials Research and Testing (BAM); Xie Xie, FCA US LLC; Gongyao Wang, Globus Medical
Thursday 2:00 PM
February 27, 2020
Room: Cardiff
Location: Marriott Marquis Hotel
Session Chair: Jörg Löffler, ETH Zurich; Chandra Sekhar Meduri, University Of Texas At Dallas
2:00 PM Invited
Effects of Testing Temperature and Sample-size on Tensile Deformation of Metallic Glass: Chandra Meduri1; Golden Kumar2; 1Texas Tech University; 2The University of Texas at Dallas
Deformation of nanoscale metallic glasses has attracted increasing attention but remains controversial due to difficulty in fabrication and testing of small samples. Here, we report the effects of systematic variation in sample-size and testing temperature. Pt-based metallic glass samples with varying diameters (100 nm -500 m) were prepared by thermoplastic drawing. Multiple samples were deformed at different temperatures and the fracture morphologies were characterized using SEM. The results show that the fraction of vein-like morphology decreases with decreasing sample size and mirror-like fracture surface was observed in samples smaller than about 2 m in diameter. With further decreasing diameter, transition from shear-localized to necking was observed and the extent of neck increased with decreasing sample diameter. The lowering in temperature had similar effect as decrease in sample diameter. This temperature-size equivalence is discussed in terms of temperature rise and formation of liquid-like layer in shear bands.
2:20 PM
Effect of Thermal History on Crystallization Kinetics of a Bulk Glass-forming Liquid: Güven Kurtuldu1; Jörg Löffler1; 1Laboratory of Metal Physics and Technology, Department of Materials, ETH Zürich
Initial phase selections by competing processes of nucleation and growth play a central role in the overall microstructural evolution during solidification. At high undercoolings before crystallization or devitrification of the liquid, heterogeneous nucleation on catalytic sites determines the nucleation onset and initial phase selection. While rapid quenching of the melt, glass fluxing, and containerless processing are the most commonly used methods for achieving large undercoolings, thermal cycling of the melt also reveals remarkable success. The effect of thermal cycling is generally attributed to the removal of heterogeneous nucleation sites. Here we demonstrate how thermal cycling, or more specifically thermal history, change the glass-forming ability reversibly. Fast differential scanning calorimetry is used to impose a certain thermal path to change the nucleation kinetics and to concurrently measure the critical cooling rate for glass formation before and after the thermal path.
2:40 PM
Corrosion Behavior of SAM2×5 Amorphous Steel / Crystalline in situ Composite: Nada F. Qari1; Arash Yazdani1; Darren Dewitt1; Javier E. Garay1; Olivia Graeve1; 1University of California, San Diego
SAM2×5 is an Fe-based bulk metallic glass with a chemical composition of Fe49.7Cr17.7Mn1.9Mo7.4W1.6B15.2C3.8Si2.4 and a significantly higher corrosion resistance compared to stainless steel. We have prepared dense samples of this alloy using spark plasma sintering at varying temperatures ranging from 630 to 675°C and whose crystallinity percentages were 21 wt.% to 82 wt.%. The corrosion rate of specimens was measured in a 3.5% NaCl solution. It was found that by enhancing sintering temperature and consequently crystallinity percent, the corrosion rate increased from 7.47 mpy (miles per year) to 15.75 mpy. Results of scanning electron microscopy show that there is no significant microstructural change in the amorphous matrix after corrosion test, while the crystalline regions are severely corroded. Although the corrosion rate increases with increasing percent crystallinity, it is still considerably lower than the control stainless steel sample which yields a corrosion rate of 28.93 mpy under the same conditions.
3:00 PM
Crystallization during Welding of Bulk Metallic Glasses: Martin Dickey1; Cody Bowman1; Timothy Pickle2; Kayode Oyedemi3; Anthony Slater4; Nicholas Hutchinson5; Richard Baumer6; 1Newport News Shipbuilding; 2Colorado School of Mines; 3ARCOTEQ; 4Cambridge Vacuum Engineering; 5Eutectix; 6LeTourneau University
Bulk metallic glasses (BMGs) possess high yield strength and corrosion resistance and are attractive for structural applications. However, BMGs are presently not widely utilized in structural applications in part due to crystallization and/or cracking induced by fusion welding processes. In this work, an analytical heat flow model for welding is utilized to propose a figure-of-merit for weldability of BMGs based upon material-specific critical heating rates and critical cooling rates necessary to avoid crystallization. Gas tungsten arc and electron beam welding results on Vitreloy 106a [Zr70Cu13Ni9.9Al3.65Nb3.4 (wt%)] are reported for various welding process conditions and compared to predictions of the weldability model. Initial results suggest that welding-induced crystallization cannot be fully explained by critical heating rate and critical cooling rate crystallization mechanisms alone. Alternative mechanisms will be discussed.
3:20 PM Break
3:40 PM Invited
Shear Band Nucleation Kinetics in Metallic Glasses: Meng Gao1; John Perepezko1; Junqiang Wang2; 1University Of Wisconsin-Madison; 2Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences
The development of shear bands is recognized as the primary mechanism in controlling the plastic deformability of metallic glasses. However, the kinetics of the nucleation of shear bands has received limited attention. The nucleation of shear bands in metallic glasses (MG) can be investigated using a nanoindentation method to monitor the development of the first pop-in event that is a signature of shear band nucleation. The analysis of a statistically significant number of first pop-in events demonstrates the stochastic behavior that is characteristic of nucleation and reveals a multimodal behavior associated with local spatial heterogeneities. The shear band nucleation rate of the two nucleation modes and the associated activation energy, activation volume, and site density were determined by loading rate experiments and related the β relaxation. The identification of the rate controlling kinetics for shear band nucleation offers guidance for promoting plastic flow in metallic glass.
4:00 PM Cancelled
Characterization of Failure Mechanisms in a Metallic/Bulk Metallic Glass Composite: Ashraf Bastawros1; 1Iowa State University
A novel experimental configuration was devised to monitor the deformation mechanisms in composite metallic glasses at the microscopic scale. A warm extruded sample of zirconium based BMG and 40% brass is utilized. The experiment is comprised of a wedge like cylindrical indenter while monitoring the evolution of the associated plastic zone, and crack initiation and propagation by a microscopic digital image correlation system. The critical contact pressure for crack initiation showed a dependence on the indenter radii. A measure of fracture toughness of the composite was reliably deduced from these measurements. Crack bridging with localized plastic deformation in the brass reinforcement was more prevailed than initiation and arrest of multiple shear bands in the BMG phase alone. The measurements and in-situ observations shed lights on the micromechanisms of deformation in BMG alloys.
4:20 PM Invited
The Effect of Thermal and Mechanical Cycling on Atomic Structure and Fracture Toughness of Metallic Glasses: Jittisa Ketkaew1; Sebastian Kube1; Derek Kuldinow1; Rui Yamada2; Hui Wang3; Wojciech Dmowski3; Takeshi Egami4; Jan Schroers1; 1Yale University; 2Frontier Research Institute of Interdisciplinary Science (FRIS), Tohoku University; 3University of Tennessee; 4University of Tennessee, Oak Ridge National Laboratory
Recently, thermal cycling was discovered as a means to rejuvenate metallic glasses, leading to a glass of higher energy, which is often associated with improved mechanical properties such as plasticity and ductility. Despite numerous studies carried out, the underlying mechanism leading to rejuvenation is still unclear. We present a systematic study of the effect of thermal cycling between the room and cryogenic temperatures and mechanical cycling with maximum load comparable to the yield strength on the fracture toughness for Zr44Ti11Cu10Ni10Be25 and Pd43Cu27Ni10P20 BMGs of various glassy states quantified by their fictive temperatures. Our study reveals that both thermal and mechanical cycling results in a non-monotonic behavior, and in addition to the rejuvenation, relaxation occurs in some cases as a consequence of both cycling methods. We will discuss similarities and differences contribution that thermal and mechanical have on the microscopic changes of BMGs which leads to the effects on fracture toughness.
4:40 PM
Nanoscale Heterogeneity on Mechanical Performance of
Cu-Zr-Al Thin Film Metallic Glasses: Xiao Han1; Yucong Gu1; Feng Yan1; Lin Li1; 1University of Alabama
The influence of nanoscale heterogeneity on the mechanical behaviors of metallic glasses is investigated by combining experimental and modeling approaches. Specifically, we deposited Cu46Zr46Al8 thin film metallic glasses (TFMGs) with different thicknesses by direct current magnetron sputtering method. Dynamic Force Microscope (DFM) revealed the nanoscale mechanical heterogeneity that could be linked to structural and chemical heterogeneities in these TFMGs. The modulus and hardness were further measured by nanoindentation. A mechanistic understanding between the nanoscale variation and mechanical properties is provided by a mesoscale shear transformation zone dynamics model. Such thickness dependent property variation can potentially be used to tailor the TFMGs for multifunctional applications.