Innovations in High Entropy Alloys and Bulk Metallic Glasses: An SMD & FMD Symposium in Honor of Peter K. Liaw: Bulk Metallic Glasses and Other Materials
Sponsored by: TMS Functional Materials Division, TMS Structural Materials Division, TMS: Alloy Phases Committee
Program Organizers: Michael Gao, National Energy Technology Laboratory; E-Wen Huang, National Chiao Tung University; Yanfei Gao, University of Tennessee-Knoxville; Robert Maass, Federal Institute of Materials Research and Testing (BAM); Hahn Choo, University of Tennessee; Yunfeng Shi, Rensselaer Polytechnic Institute; Soo Yeol Lee, Chungnam National University; Xie Xie, FCA US LLC; Gongyao Wang, Globus Medical; Liang Jiang, Yantai University
Tuesday 2:00 PM
February 25, 2020
Room: Marina Ballroom G
Location: Marriott Marquis Hotel
Session Chair: Robert Maass, University of Illinois at Urbana-Champaign; Shan Cecilia Cao, University of West Florida
2:00 PM Invited
Melting of Metallic Glasses in the Limit of Ultra-high Liquid Fragility: William Johnson1; 1California Institute of Technology
The glass transition is commonly viewed as a dynamic transition involving a dramatic slowing of configurational rearrangements in the liquid state at deep undercooling. The question of whether an underlying thermodynamic transition exists has been the subject of long standing debate. Recently, both experiments and MD simulations reveal that metallic glasses exhibit first order melting behavior in the limit of ultrahigh fragility. The solid glass melts to a fluid liquid state in the same manner as a crystal melts. The origin of this behavior can be traced to the collapse of elastic rigidity of the solid glass. The experimental evidence for this first order thermodynamic glass transition will be presented and discussed.
2:25 PM Invited
Glass Formation with Monodisperse Colloids: Frans Spaepen1; 1Harvard University
The conditions for formation of single-component metallic glasses and their stability are fascinating and long-standing problems in glass science. It is therefore of interest that it is possible to form stable glasses with monodisperse (i.e., single-size) colloidal particles. These are particles in suspension, which form phases similar to those formed by atoms. Since the particles are “fat” (~1µm) and “slow” (~10Hz), they can be individually tracked by confocal microscopy. This makes it possible to follow crystallization, melting and glass formation on the particle level.This talk will review the experimental conditions for formation of these colloidal glasses, as well as their stability against crystallization. The colloidal technique also makes it possible to observe both homogeneous nucleation as well as growth of crystals from the liquid on the particle level. The results will be compared to existing kinetic models and their implications for glass formation will be analyzed.
2:50 PM Invited
Structure Modulation for Plasticity Enhancement of Metallic Glasses: Jurgen Eckert1; 1Erich Schmid Institute of Materials Science; Montanuniversität Leoben
The intrinsic properties of metallic glasses are strongly affected by the details of short- and medium-range order cluster motifs, and their response to external fields like mechanical deformation or temperature cycling largely depends on local atomic rearrangements triggered by or causing heterogeneous stress and strain variation on different length-scales.This talk explores the structural diversity that can be achieved in metallic glasses considering structure changes, recovery and rejuvenation mechanisms, as well as phase separation or nanocrystallization phenomena when the materials are subjected to different casting conditions, mechanical deformation, thermo-mechanical cycling or net-shaping. The findings from experiments and simulations will be discussed with respect to short- and medium-range order modulation, local stress and strain states, defect generation and annihilation, and precipitation of secondary phases. The structure changes will be correlated with plastic deformability and failure mechanisms, and the effectiveness of composition tuning and thermo-mechanical processing for plasticity improvement and possible strain hardening will be discussed.
3:10 PM Invited
Serrated Flow and Beyond: Strain Localization in Metallic Glasses: Robert Maass1; 1University of Illinois at Urbana-Champaign
At low homologous temperatures, metallic glasses (MGs) admit limited plasticity via strain localization by so-called shear bands. Shear-bands are spatially confined to the nanometer scale, are active at very short time-scales, and leave only a faint signature of structural damage relative to the surrounding matrix. For decades, research has focused on revealing fundamental properties of shear bands, with the goal of identifying properties that may help us to design more ductile MG-alloys. In this talk, we discuss how fundamental properties of shear bands are linked to the macroscopic appearance of plastic flow. We will address the spatial signature of a shear bands and show that it is much more complex than the nano-scale core. Finally, our talk will cover the structural evolution of shear bands with plastic stain, which we believe represents one of the main unsolved questions in the area of shear banding in MGs.
3:30 PM Invited
The Structure and Deformation Behaviors of Annealed Cu-Zr Metallic Glasses: Cang Fan1; Xingxing Yue2; P. K. Liaw3; 1YMT Simulations LLC; 2Nanjing University of Science & Technology; 3University of Tennessee
The structure evolution of annealing as-cast Cu-Zr metallic glasses (Cu36Zr64, Cu50Zr50, and Cu64Zr36) was investigated using the molecular dynamics simulations. The results show that the Cu64Zr36 metallic glass was partially crystallized under the annealing process. The crystallized structure is Cu2Zr Laves phase, which consists of Cu-centered <0 0 12 0> and Zr-centered <0 0 12 4> clusters. The simulations of the uniaxial compression tests were conducted on as-cast and annealed Cu64Zr36 at 300 K for investigating the initiation and propagation of their shear bands. The results showed that the shear band occurred only in the annealed sample. During deformation, the fraction of the Cu2Zr laves phase in the shear band dramatically decreases when the stress suddenly decreases. However, its fraction in the matrix changes slightly. The destruction of Cu-centered <0 0 12 0> and Zr-centered <0 0 12 4> clusters is accompanied by the annihilation of the Cu2Zr Laves phase.
3:50 PM Break
4:05 PM Invited
Metallic Glasses: From Coatings to Their First-ever Nanotube Arrays: Jinn Chu1; 1National Taiwan University of Science and Technology
Thin film metallic glass (TFMG) is a new class of multi-component metallic thin film with unique characteristics, including high strength, high ductility, and low coefficient of friction, though their bulk forms are already well-known for properties because of their amorphous structure. Thin films prepared by physical vapor-to-solid deposition are expected to be further from equilibrium than those prepared by liquid-to-solid melting or casting processes. This is expected to further improve the glass forming ability. In the first part of my talk, I will present some important TFMG properties and applications we have discovered in recent years. Then, the metallic glass nanotubes fabricated by a simple lithography and sputter deposition process for very large-scale integration is introduced. This first-ever metallic nanotube array is awarded by American Chemical Society (ACS) at nano tech Japan 2018 in Tokyo. Many of their exceptional properties will be presented.
4:25 PM Invited
Rejuvenation by Fatigue: Takeshi Egami1; 1University of Tennessee
Metal fatigue is a very important subject for which numerous contributions by P. K. Liaw are well-known. For crystalline metals and alloys fatigue leads to crack formation and failure, which can be catastrophic. Metallic glasses also fail by fatigue, but the microscopic mechanisms are different. In glasses defects, such as shear-transformation zones (STZs), are not topologically protected and disappear after activation. For this reason metallic glasses do not show work-hardening. Instead it is now known that the glass locally melts for a short time (~ ps) during the activation of STZ. This results in local rejuvenation to a more disordered ductile state. Therefore fatigue can lead to rejuvenation. However, shear bands and cracks formed by fatigue can shorten the life of metallic glass as a structural material. These should enter the alloy design strategy for better metallic glasses. This work is supported by the DOE-BES-MSED.
4:45 PM Invited
Mechanical Modeling and Plasticity of Bulk Metallic Glasses: Hyoung Seop Kim1; 1Pohang University of Science and Technology
The mechanical properties of engineering materials are key for ensuring safety and reliability. However, the plastic deformation of BMGs is confined to narrow regions in shear bands, which usually result in limited ductilities and catastrophic failures at low homologous temperatures. The quasi-brittle failure and lack of tensile ductility undercut the potential applications of BMGs. In this presentation, we present clear tensile ductility in a Zr-based BMG via a high-pressure torsion (HPT) process. Enhanced tensile ductility and work-hardening behavior after the HPT process were investigated, focusing on the microstructure, particularly the changed free volume, which affects deformation mechanisms (i.e., initiation, propagation, and obstruction of shear bands). Our results provide insights into the basic functions of hydrostatic pressure and shear strain in the microstructure and mechanical properties of HPT-processed BMGs.Mechanical modeling and finite element analysis are presented.
5:05 PM Invited
Serrated Yielding in an Iron-chromium-aluminum (FeCrAl) Alloy Tubing: Mahmoud Hawary1; Abdullah Alomari1; K. Murty1; 1North Carolina State University
An iron-chromium-aluminum (FeCrAl) Kanthal® APMT alloy is one of the candidate cladding material for water reactors to serve as a substitute for zirconium-based alloys with enhanced accident tolerance and improved high-temperature properties along with oxidation/corrosion resistance. In this study, serrated yielding behavior resulting from the dynamic strain aging (DSA) of FeCrAl APMT alloy is investigated over the temperature range (298 – 973 K) and strain rates [10^(-3)-10^(-5) sec^(-1)] using uniaxial tensile tests followed by microstructure examinations for the as-received and deformed samples. Temperature and strain rate effects on tensile properties and serration types are evaluated along with critical strains for serrated flow.
5:25 PM Invited
Creep Resistance of a Hierarchical-precipitate-strengthened Ferritic Alloy: Gian Song1; Soon Jik Hong1; Jin Kyu Lee1; Sung Ho Song1; Sung Hwan Hong2; Ki Buem Kim2; Yanfei Gao3; Zhiqian Sun3; Peter Liaw3; 1KongJu National University; 2Sejong University; 3University of Tennessee
Hierarchical NiAl/Ni2TiAl-precipitate-strengthened ferritic alloys have been developed by adding Ti into a previously-studied NiAl-precipitate-strengthened ferritic alloy. A systematic investigation has been conducted to study the interrelationships among the composition, microstructure, and mechanical behavior, and provide insight into deformation micro-mechanisms at elevated temperatures. The microstructural attributes of hierarchical ferritic alloys contain a two-phase NiAl/Ni2TiAl precipitate, which is coherently distributed in the Fe matrix. The creep resistance is significantly improved than the NiAl-strengthened ferritic alloy without the Ti addition. The microstructural evolution of precipitates during heat treatment is investigated using transmission-electron microscopy and atom-probe tomography are used to study the precipitate evolution, such as the size, morphology, composition of the precipitates. It was found that the hierarchical structure within the precipitate evolves from the fine two-phase-coupled to agglomerated coarse structures, as the aging time increases. Moreover, transition from the coherency to semi-coherency is concomitant with that of hierarchical structure within the precipitate.