Bulk Metallic Glasses XIV: Structures and Mechanical Properties III
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

Wednesday 8:30 AM
March 1, 2017
Room: 33A
Location: San Diego Convention Ctr

Session Chair: John Lewandowski, Case Western Reserve University; Wojciech Dmowski, University of Tennessee

8:30 AM  Invited
Early Plasticity in Metallic Glasses: Dominik Tönnies1; Cynthia Volkert1; Lin Tian2; 1University of Göttingen; 2Universität Göttingen
    Understanding the emergence of shear bands from smaller deformation entities, such as shear transformation zones, has become a topic of intense research in the past years, with the goal of ultimately mediating the brittle behavior the shear bands cause. However, since shear transformation zones as well as shear bands may operate at time and length scales that are barely accessible experimentally, systematic studies must often be performed to gain indirect insight. Here, we present several small-scale mechanical studies on metallic glasses which have been designed to test our understanding of the emergence of shear bands. We vary specimen size, strain rate, acquisition rate, and stress state in microcompression or spherical nanoindentation studies, and by analyzing the mechanical response and the distributions of strain bursts, infer certain limits on the inherent behavior of emerging shear bands and the cooperativity of the shear transformation zones.

8:50 AM  Cancelled
A Comparative Analysis of Metal-Ni-P Metallic Glasses Synthesized via Electroless Plating: Phil Meagher1; Manuel Abad1; David Browne1; 1University College Dublin
    Electroless plating is an auto-catalytic technique carried out in an aqueous solution, used to evenly plate metallic coatings onto geometrically complex and non-conductive substrates. The authors recently reported a novel technique for producing amorphous structures with high shape complexity, by plating a Nickel-Phosphorous alloy onto additively manufactured polymer cores and selectively leaching the polymer. In the current work, the authors present techniques for synthesis and composition control of glassy Metal-Ni-P alloys via electroless plating on various substrates. Furthermore, tribological, mechanical, and structural investigations are made on the alloys via XRD, DSC, SEM, nanoindentation, and wear testing. Finally, comparisons are drawn with their BMG alloy counterparts in the as-cast state.

9:10 AM  Student
Thermal Structural Evolution of Zr-based Metallic Glasses and Liquids Investigated by High Energy X-ray Diffraction and Inelastic Neutron Scattering: Zengquan Wang1; Wojciech Dmowski1; Yang Tong1; Takeshi Egami1; Adam Vogt2; Kenneth Kelton3; 1University of Tennessee, Knoxville; 2Oak Ridge National Laboratory; 3Washington University in St. Louis
    In this work, the structural evolutions of Zr65Cu17Ni8Al10 and Zr80Pt20 metallic glass samples were studied by in-situ high energy X-ray and neutron diffraction. X-ray patterns were collected from RT up to 1300 K and the structure functions and PDFs were analyzed. Glass transition, nano-crystallization, and liquid transition were observed in the Zr65Cu17Ni8Al10 sample during the heating. The extrapolated structure function changes smoothly from the supercooled region to the liquid state. In the Zr80Pt20 sample, a transition is observed at 430 oC resulting in nano-crystalline phase, and another phase transition is observed at higher temperature. Furthermore, the local dynamics in Zr80Pt20 liquid were studied by inelastic neutron scattering with electro-static levitation. Combining with molecular dynamics simulation, the different thermal structural evolutions are tentatively explained by the topological and chemical effects of the atomic pairs in these alloys.

9:30 AM  Invited
Pressure Dependence in Mechanical Properties of Metallic Glasses near the Glass Transition: Zachary Aitken1; Mehdi Zadeh1; John Lewandowski2; Yong Wei Zhang1; 1Institute of High Performance Computing, A*STAR; 2Case Western Reserve University
    In contrast to predictions of various classic yield criteria, metallic glasses experimentally display pressure dependence at temperatures that are a significant fraction of their glass transition temperature. This dependence manifests as an increase in the fracture strength with increasing hydrostatic pressure along with a transition from a ductile to brittle failure mode. It is currently unclear to what extent the combined effect of temperature and pressure has on the microstructure of the metallic glass and how this is reflected in the mechanical response of the bulk metallic glass. In this talk we report the results of a study on the mechanical behaviour of a metallic glass near its glass transition temperature and under applied pressure. We report the temperature and pressure dependence of the elastic properties and dominant deformation mechanism and discuss these results in context of the short and medium range order as revealed through molecular dynamics simulations.

9:50 AM  Invited
Pressure-induced Structural Change in Liquid Eutectic Ga85.8In14.2 Alloy: Qing Yu1; Xiaodong Wang1; Yu Su1; Azkar Saeed Ahmad1; Qingping Cao1; Dongxian Zhang1; Jianzhong Jiang1; 1Zhejiang University
    The structure of liquid eutectic Ga85.8In14.2 alloy was investigated up to a pressure of 13 GPa using synchrotron radiation x-ray diffraction in a diamond anvil cell combined with ab initio molecular dynamics (AIMD) simulation. The diffraction patterns revealed that the liquids crystallized into monoclinic phase in the vicinity of 3.0 GPa, which is in agreement with theoretical calculation. Further an increase in pressure resulted in rapid transformation of the high-pressure phase with triclinic structure until the monoclinic phase became completely transformed at 13 GPa. Besides, the high pressure phase can persist in this structure upon decompression to 3.7 GPa and become liquids by passing the transformation into the low pressure crystal. Static structural factor S(q) before and after compression indicated no structural changes in liquid GaIn alloy. Furthermore, AIMD calculation was performed to study the pressure-induced crystallization of liquid GaIn alloys and shed light on the an atomistic transformation mechanism.

10:10 AM Break

10:30 AM  
Revealing Homogeneous Plastic Deformation in Ti-based Metallic Glass Composites with Dendrites under Tension: Fufa Wu1; 1Liaoning University of Technology, China
    The tensile plastic deformation of dendrite-reinforced Ti-based metallic glass composites (MGCs) was investigated. It was found that there exists a critical normalized strain-hardening rate (NSHR) that determines the plastic stability of MGCs: if the NSHR is larger than the critical value, the plastic deformation of the MGCs will be stable, i.e. the necking and strain localization can be effectively suppressed, resulting in homogeneous plastic elongation in MGCs. Meanwhile, dendrite-reinforce MGCs are verified to be intrinsically ductile, and can be use as good coating for improve the surface properties of pure titanium or titanium alloys. These findings are helpful for designing, producing, and using MGCs with excellent performance properties.

10:50 AM  Invited
Plasticity of In-situ Ti-based Metallic Glass Matrix Composites: Jean-Marc Pelletier1; S. Cardinal1; Jichao Qiao2; 1INSA-Lyon; 2Northwestern Poltechnical University
    In order to improve the limited plasticity of bulk metallic glasses, the main idea is to introduce some inhomogeneity, ranging from atomic scale to micrometer scale. Two main routes have been reported in the literature to introduce this inhomogeneity: either by monitoring the chemical composition so as to induce a controlled and limited crystallization during the solidification phenomenon (in-situ composites) or by introducing crystalline particles which are not modified during the manufacturing of the bulk metallic glass matrix (ex-situ composites). Both methods offer advantages and drawbacks. The development of MGMC has been reported mainly in the Zr-based metallic glasses, and more recently in Ti-based alloys. The aim of the present work is to compare Ti-based MGMC produced by direct solidification with more conventional Ti-based BMG. The mechanical properties of these materials are characterized, mainly those corresponding to the plastic behavior.

11:10 AM  Invited
Homogeneous Plastic Deformation of Metallic Glasses at Room Temperature: Yi Li1; 1Institute of Metal Research
    Usually, plastic deformation of large-sized metallic glasses (MGs) is highly localized into shear band under uniaxial stress. Due to this, softening would occur inside the shear bands and the plastic deformation is heterogeneous. Here we shall report a way to suppress the shear banding and found that the deformation behaviour of metallic glasses would be expected to be quite different at room temperature In our talk, we will show that bulk metallic glasses are capable homogeneous plastic flow at room temperature under either tension or compression. The mechanism for such a difference will also be discussed.

11:30 AM  Student
Investigation of the Stability of Newtonian Viscous Flow in Various Metallic Glass Systems: Hyun Seok Oh1; Chae Woo Ryu1; Eun Soo Park1; 1Seoul National University
    Viscous flow has been recognized as the unique properties of metallic glass, as it enables thermoplastic forming (TPF) for near-net shape forming process. Recently, the phenomenon is becoming increasingly important as it contributes to the plastic deformation not only in supercooled liquid region(SCLR) but in lower temperature region. Therefore, investigation of viscous flow is essential to get perspective for the general deformation behavior of metallic glass. Meanwhile, viscous flow can be divided into two regions, which are Newtonian and non-Newtonian, regarding the stability of flow. In this research, we aim at providing an extended concept to understand the TPF ability of metallic glass considering the stability of Newtonian viscous flow. Correlation between stability of Newtonian viscous flow and other characteristic parameters of metallic glass will be systematically discussed. Our foundation will enhance the general understanding of mechanical behavior of metallic glass, which is based on with liquid or liquid-like flow.

11:50 AM  
Production of Zirconium Based Bulk Metallic Glass Sheet: Daniel East1; Nicholas Hutchinson2; Jim Yurko2; Robert Haun3; 1CSIRO; 2Materion; 3Retech Systems
    Sheet measuring 1mm x 75mm x 2m has been produced from alloys Vit106 and 105 via twin roll casting. Twin roll casting is a production process that is used to produce sheet metal directly from a melt. To prevent the oxidation of the sheet the casting process is performed within a chamber containing an inert atmosphere. To successfully cast strip with an amorphous structure the heat flow of the casting process is controlled. If the cooling is such that regions of the sheet exit the rolls at a temperature above the nose of the continuous cooling transformation diagram then a crystalline structure will be produced. If the exit temperature of the sheet is lower than the glass transition temperature of the alloy then the load on the casting mill will increase to a level that the rolls will stall.

12:10 PM  
Structure-property Relationships in Nanoporous Metallic Glasses: Daniel Sopu1; Celal Soyarslan2; Mihai Stoica1; Jürgen Eckert3; 1IFW Dresden; 2Hamburg University Technology; 3Erick Schmid Institute of Materials Science
    Despite the great potential of bulk metallic glasses (BMG) to be used as structural materials, the inverse strength-ductility-functionality problem significantly limits the application of these materials. However, premature failure can be avoided if heterogeneities are introduced into the glassy matrix. Within this study, we present a new strategy to improve the ductility of BMG by constructing 2-dimensional heterostructures like nanoporous BMG. By using molecular dynamics and finite element simulations an effective strategy to control the strain localization in CuZr BMG heterostructures is provided. Depending on the pore architecture in the heterostructure, upon uniaxial tension, nanoporous BMG show a wide range of failure modes ranging from brittle to ductile ones. These findings are helpful in understanding the structure-property relationships of complex BMG composites reinforced with a systematic secondary phase design on the nano-level.