Bulk Metallic Glasses XIV: Mechanical and Other Properties II
Sponsored by: TMS Structural Materials Division, TMS: Mechanical Behavior of Materials Committee
Program Organizers: Peter Liaw, University of Tennessee; Hahn Choo, University of Tennessee; Yanfei Gao, University of Tennessee; Yunfeng Shi, Rensselaer Polytechnic Institute; Xie Xie, The University of Tennessee; Gongyao Wang, The University of Tennessee; Jianzhong Jiang, Zhejiang University

Thursday 2:00 PM
March 2, 2017
Room: 33B
Location: San Diego Convention Ctr

Session Chair: Rainer Wunderlich, Ulm University; Gary Shiflet, University of Virginia

2:00 PM  Invited
Thermophysical Properties of the Zr-based Bulk Metallic Glass Forming Alloy VIT106a in the Liquid Phase on the Ground and on ISS: Rainer Wunderlich1; Anup Gangopadhyay2; Christopher Pueblo2; Kenneth Kelton2; Hans Fecht1; 1Ulm University; 2Washington University
    VIT106a is a Zr-based bulk metallic glass forming alloy with composition Zr58.5 Ni12.8 Al10.3 Cu15.6Nb2.8. Thermophysical properties in the stable and undercooled liquids were investigated under containerless processing conditions in an electromagnetic levitation device under reduced gravity conditions. Non-contact modulation calorimetry was applied for the evaluation of the specific heat capacity and thermal transport properties such as the total hemispherical emissivity and an effective thermal conductivity. The surface tension and viscosity were measured by the oscillating drop method. The specific heat capacity as a function of temperature exhibited a discrete maximum at about T=1200 K. This temperature is close to a temperature where a change in the x-ray structure factor, S(q), was observed in ground based experiments, possibly indicating a change in the medium-range order of the liquid. Such a change is also reflected in the temperature dependence of the convective contribution to internal heat transport.

2:20 PM  Invited
Degradation Behavior of Bulk Metallic Glasses – Corrosion, Erosion, and Wear: Ayyagari Aditya1; Sundeep Mukherjee1; 1University of North Texas
    Bulk metallic glasses show excellent surface properties such as high resistance to corrosion, erosion, and wear. These characteristics are simplistically attributed to their uniform amorphous structure with no grain boundaries, high hardness, and chemical inertness. However, the intricacies of the mechanisms are often ignored and are of paramount importance to fundamentally understand amorphous alloys. For example, the corrosion behavior may change dramatically with slight change in chemistry even though the amorphous structure is maintained. There are similar reports on wear behavior. We compared the surface properties of several BMGs with processing conditions ranging from surface rejuvenation to thermal relaxation. This provided valuable insights into the role of chemistry, free volume, and surface state on the degradation behavior of BMGs.

2:40 PM  Cancelled
Effects of Ion Irradiation on the Mechanical and Microstructural Properties of Two Different Bulk Metallic Glass Alloys: Jamieson Brechtl1; Hongbin Bei2; Steven Zinkle1; 1University of Tennessee; 2Oak Ridge National Laboratory
    Bulk metallic glasses (BMG) are thought to be less susceptible to irradiation displacement damage since they contain an amorphous structure which prohibits the formation of Frenkel defects. This potential resistance to deleterious microstructural changes therefore makes BMGs a possible candidate for use in irradiation environments. However, relatively little is known about their irradiation behavior. Nanoindentation mechanical property tests were performed on as-cast, annealed and ion irradiated (9 MeV Ni2+, 4.5 MeV B+) Zr52.5Cu17.9Ni14.6Al10Ti5 (BAM-11) and Cu60Zr20Hf10Ti10 BMG after midrange doses of 1 and 10 dpa at room temperature and ~370 oC using Berkovich and spherical indenters in order to evaluate hardness, Young’s modulus and “soft zone” defect densities. Two different ions were used to investigate potential primary knock on atom spectrum effects. Extended x-ray fine absorption spectroscopy was used to investigate effects of displacement damage on the short range order of the alloys.

3:00 PM  Invited
Electronic Mechanism of Ductile-to-Brittle Transformation in Amorphous Calcium-based Alloys: Andrew Cheung1; Gary Shiflet1; 1University of Virginia
    Atomic bonding plays a crucial role in determining ductility for calcium-based bulk metallic glass systems. When calcium forms ionic bonds, metallic glasses are brittle. When calcium does not readily share its electronic charge, the BMG can be ductile. Various gas exposures reveal that ductile calcium glass systems rapidly turn brittle with exposure to water vapor; with relative humidity exposure levels >70% the ductile-to-brittle transformation is observed in under a minute. New ionic bonds between calcium and hydrogen forming calcium hydrides are the cause of the embrittlement. The source of atomic hydrogen is a byproduct of the surface reaction between water vapor and calcium, forming calcium hydroxide. The presentation will report on chemical reaction kinetics of calcium compound formation including calcium-carbonate, hydroxide and hydride. The transfer of charge from calcium atoms through the introduction of hydrogen into the system and subsequent phase transformations will be detailed using SIMS, XPS and TEM.

3:20 PM Break

3:40 PM  
Material Behavior in Micro Milling of Zirconium based Bulk Metallic Glass: Boyuan Xie1; Maroju Kumar1; David Yan2; Xiaoliang Jin1; 1Oklahoma State University; 2University of Wisconsin-Green Bay
    Bulk metallic glasses (BMGs) are a group of metallic materials with amorphous microstructure. BMGs have been increasingly used in various applications such as optical molds, sport equipment and biomedical components. The machining mechanism for the BMGs is distinct from that of the crystalline metal alloys due to the differences in their microstructures and mechanical properties. This paper presents experimental investigations on the material behavior in micro milling of zirconium based bulk metallic glass (Zr-BMG). Micro milling of the BMG with high spindle speed up to 105,000 rpm was conducted. Surface morphology, microstructural evolution and crystallization of the machined surface were characterized by optical and scanning electron microscopy, X-Ray diffraction and energy dispersive X-Ray spectroscopy. The results detailed the responses of the Zr-BMG to the milling conditions which enables the machining conditions to be optimized to achieve an improved surface quality and machining efficiency.

4:00 PM  
The Corrosion and Wear Behaviors of a ZrCuNiAl Bulk Metallic Glass in Simulated Groundwater: Yongjiang Huang1; Hongbo Fan1; Jing Liu1; Zhiliang Ning1; Jianfei Sun1; 1Harbin Institute of Technology
    Here, a Zr50.7Cu28Ni9Al12.8 (at %) bulk metallic glass was selected as the model materials. The alloy samples with different crystallization volume fraction (Vf) were obtained via isothermal annealing above glass transition temperature. Both the corrosion and wear resistance of the alloy samples in simulated groundwater firstly increased and then decreased with increasing the Vf, yielding the best corrosion resistance at 14 % Vf. The corrosion-wear relation of the ZrCuNiAl alloy samples has been interpreted from the perspective of the microstructure.

4:20 PM  Student
The Effect of Phase Transformation on the Magnetocaloric Effect in Co-based Heusler Alloys: A-Young Lee1; SongYi Kim1; Hye Ryeong Oh1; Hyun-ah Kim1; Young Do Kim2; MinHa Lee1; 1Korea Institute of Industrial Technology; 2Hanyang University
    The eco-friendly magnetic refrigerator as replacing conventional vapor compression refrigerator is based on magnetocaloric effect. The measurement methods of magnetocaloric effect are adiabatic temperature change or isothermal magnetic entropy change. In initial study, typical magnetocaloric alloys have been using crystalline materials. The alloys with the amorphous structure have many advantages such as high refrigeration capacity, broadened magnetic entropy change, better corrosion resistance, and mechanical properties for enhance endurance. Co-based magnetocaloric alloys have been considered as a novel room temperature magnetocaloric material system. In this study, we investigated the differences of the magnetic properties and magnetocaloric behaviors of Co-based amorphous alloys and crystalline alloys, respectively. The magnetocaloric properties of Co-based alloys were measured by a Quantum Design Physical Properties Measurement System (VSM, VersaLab). The structure of alloys was characterized by X-ray diffractometer (XRD, Bruker, D8 discover) using Cu Kα radiation.

4:40 PM  
Effect of Sm Micro-alloying on the Mechanical Behavior and Crystallization Kinetics of Cu-Zr-Al BMGs: Fatih Sikan1; Ilkay Kalay2; Sezer Ozerinc1; Eren Kalay1; 1METU; 2Cankaya University
    The Cu-Zr-Al BMGs show relatively high strength but they tend to deform along thin shear bands which do not allow macroscopic plasticity. Introducing crystalline constituents embedded within the glassy matrix is a promising technique to improve the ductility. In this respect, we have investigated the mechanical properties and crystallization kinetics of Sm micro-alloyed Cu-Zr-Al BMGs. Ingots of (Zr50Cu40Al10)100-xSmx (0 ≤ x ≤ 5, at. %) were produced by arc-melting and subsequently suction-cast into rods with diameters up to 3 mm. The as-solidified and partially crystalline structures were characterized by a combined study of SEM, TEM, APT, XRD and DSC. Mechanical properties and shear band stability of glassy and partially crystalline (Zr50Cu40Al10)100-xSmx (x:0-5) alloys were determined using nanoindentation and macro and micro-pillar compression tests with respect to percent crystallinity. The effect of introducing crystals within the amorphous matrix will be discussed in correlation to sample size.