Innovations in High Entropy Alloys and Bulk Metallic Glasses: An SMD & FMD Symposium in Honor of Peter K. Liaw: High Entropy Alloys: Other Properties and Modeling
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 8:30 AM
February 25, 2020
Room: Marina Ballroom G
Location: Marriott Marquis Hotel
Session Chair: Veerle Keppens, University of Tennessee; Yanfei Gao, University of Tennessee
8:30 AM Invited
Defect Dynamics and Microstructure Evolution in High Entropy Alloys: Yanwen Zhang1; Takeshi Egami2; William Weber2; 1Oak Ridge National Laboratory; 2The University of Tennessee
The effort to understand and design concentrated solid-solution alloys (CSAs), including high entropy alloys (HEAs), has prompted fundamental questions that challenge established theories and models currently applicable to conventional alloys. The current understanding of electronic and atomic effects, defect dynamics, and microstructure evolution in CSAs suggests that radiation energy dissipates at different interaction strengths via the energy carriers. Modification of electronic- and atomic-level heterogeneities and tailoring of atomic transport processes can be realized through tuning of the chemical complexity of such alloys via the selection of elements and their concentrations. Controlling energy dissipation via site-to-site chemical complexity reveals new design principles for predictive discovery and guided synthesis of new alloys of new alloys with targeted functionalities, including much increased structural strength and substantially improved radiation performance.This work was supported by EDDE, an EFRC funded by the U.S. DOE, BES.
8:50 AM Invited
Radiation Effects in High Entropy Alloys and Bulk Metallic Glasses: Steven Zinkle1; Congyi Li1; Tengfei Yang1; James Brechtl1; 1University of Tennessee
Particle irradiation is a useful tool to examine the phase stability of novel materials, due to the pronounced accelerated diffusion and atomic mixing phenomena that are induced by irradiation. Several high entropy alloys (HEAs) and bulk metallic glasses (BMGs) have been exposed to energetic heavy ion irradiation over a range of conditions ranging from room temperature to 700C and damage levels up to ~50 displacements per atom. Ion irradiation was observed to accelerate phase decomposition in some HEAs, but overall the investigated HEAs exhibited good resistance to microstructural degradation such as void swelling. The ion irradiated BMGs generally observed good phase stability (no radiation enhanced crystallization) and moderate changes in properties such as hardness and density up to ~0.8Tg where Tg is the absolute glass transition temperature. These observations will be compared with previously reported particle irradiation studies on HEAs and BMGs.
9:10 AM Invited
Energy Dissipation and Damage Evolution in Irradiated Concentrated Solid Solution Alloys: William Weber1; Eva Zarkadoula2; Yanwen Zhang2; 1University of Tennessee; 2Oak Ridge National Laboratory
Single-phase concentrated solid solution alloys (CSAs) have drawn increasing interest due to their outstanding properties, including exceptional fracture toughness at cryogenic temperatures, high strength and low plasticity at elevated temperatures, and enhanced radiation tolerance. Using computational and experimental approaches, the effects of electronic energy deposition and dissipation from energetic ions on damage production and evolution have been investigated. Electronic energy loss affects damage production in single and overlapping collision cascades (30 to 150 keV). Experimentally, the tunable chemical complexity, local lattice distortions, and nanostructured features of CSAs are exploited to control energy dissipation, defect dynamics and microstructure evolution. These results suggest a new paradigm for designing enhanced radiation tolerance. This work was supported by EDDE, an EFRC funded by the U.S. DOE, BES.
9:30 AM Invited
High Entropy Alloys as Filler Metals: Zhenzhen Yu1; Benjamin Schneiderman1; Abdelrahman Abdelmotagaly1; Chihpin Chuang2; Jianxun Hu3; 1Colorado School of Mines; 2Argonne National Laboratory; 3Honda R&D Americas, Inc.
High entropy alloys have a vast compositional space available. Their tendency to form entropy-stabilized, simple solid solution phases, and to exhibit composition-dependent sluggish diffusion characteristics, make them potential candidates as filler metals for similar and dissimilar welding and joining. Meanwhile, the complex deformation mechanisms in HEAs with a primary FCC phase enable abundant strain hardening, which could accommodate the thermally induced stress during welding. One application example is brazing of Ni-base superalloys. A new HEA filler, Mn35Fe5(CoNiCu)20, was designed and the microstructural evolution during brazing was systematically investigated by ex-situ and in-situ characterizations and kinetic analysis. An optimal shear strength comparable to that of the Alloy 600 substrate was achieved in the braze joints. Another application example is the design of HEA filler for resistance spot welding of galvannealed advanced high strength steels to mitigate the liquid metal embrittlement issue caused by expulsed liquid zinc at the joint interface.
9:50 AM Invited
Expanding High-entropy to Ceramics: Identifying High Entropy Oxides with Perovskite, Spinel, or Pyrochlore Structure: Veerle Keppens1; 1University of Tennessee
The concept of entropy stabilization has recently been expanded to oxides, realizing the first high entropy oxides (HEOs) and demonstrating that configurational disorder has the potential to enable the discovery of new materials. This talk will report on our recent efforts to engineer new ceramic materials by applying the concept of entropy stabilization to complex oxides. More specifically, by adding the chemical and structural disorder inherent to entropy-stabilized materials to the competing electronic/magnetic interactions that characterize complex oxides, we provide a new strategy for the design/discovery of materials with unique properties.
10:10 AM Break
10:25 AM Invited
Tracer Diffusion in High-entropy Alloys: the Impact of Constituents and Composition: Gerhard Wilde1; 1University of Muenster
High entropy alloys (HEA) attract an increased attention as a potential structural material due to outstanding mechanical and physical properties. With this work, we contribute to understanding the diffusion kinetics of HEA that is critical concerning their phase stability and deformation behavior, particularly at elevated temperatures. Furthermore, the influence of the phase composition on diffusion, particularly at grain boundaries in these alloys was also examined. These combined measurements directly address the debate about sluggish diffusion by investigating self-diffusion. Additionally, the diffusion coefficients for self-diffusion of the constituent elements are determined in polycrystalline HEA as a function of composition and for varying numbers of constituents in the solid solution. The impact of composition, number of constituents, nature of constituents and homologous temperature on volume and grain boundary self-diffusion are critically discussed.
10:45 AM Invited
High-throughput Predicting and Machine-learning Solid-solution Formation: Michael Gao1; Zongrui Pei1; Junqi Yin2; Jeffrey Hawk1; David Alman1; 1National Energy Technology Laboratory; 2Oak Ridge National Laboratory
Various empirical rules are proposed to predict the formation of single-phase solid solution, but they are based on very small datasets and hence are of very limited predictability. In this work, we perform a machine-learning (ML) study on a large dataset consisting of 1252 alloys, including binary and high-entropy alloys, and we achieve a success rate of 93% in predicting single-phase solid solution. The present ML results suggest that the molar volume and bulk modulus are the most important features, and accordingly, a new physics-based thermodynamic rule is constructed. The new rule employs only the elemental properties and is nonetheless slightly less accurate (73%) than the ML algorithm. Finally, the advantages and pitfalls in applying high-throughput screening and ML versus CALPHAD calculations will be discussed.
11:05 AM Invited
Microstructure Evolution with Temperature in the Al-rich High-entropy Alloys: Louis Santodonato1; 1Advanced Research Systems
The integration of experimental and theoretical techniques is strongly emphasized in the research group of Prof. Peter K. Liaw. On the experimental front, in situ heating with neutron scattering, neutron imaging, and scanning transmission electron microscopy (STEM) have played big roles in the study of high-entropy alloys (HEAs). This experimental work has been complimented by theoretical simulations of HEA atomic mixing behaviors, using techniques such as Monte Carlo and Molecular Dynamics simulations. The present talk describes how these techniques were used to investigate the microstructural evolution with temperature and time in the AlxCoCrCuFeNi alloys. Although the microstructural evolution appears quite complex, the major trends may be understood and modeled in terms of the redistribution of atoms on a simple lattice, producing coherent phase mixtures, similar to nickel-based superalloys.
11:25 AM Invited
Nature of Metallic Bonding in Bulk Metallic Glasses and High Entropy Alloys: Wai-Yim Ching1; 1University of Missouri
I discuss the nature of metallic bonding in bulk metallic glasses and high entropy alloys. I advocate the use of total bond order density (TBOD) as a fundamental metric to assess the atomic scale structure and internal cohesion of these two complex systems. The approach used is to first construct large structure models of sufficient size and fully optimize the structure with no constraints. This is followed by detailed DFT calculation of the electronic structure and interatomic bonding between every pairs of atoms in the model. The TBOD is obtained by summing up all bond order values of atoms in the model and normalized by its volume. Results are presented for: (1) Vitreloy Zr41.2Ti13.8Cu12.5Ni10Be22.5 and (2) Ceramic composite model between HEA TiNbTaZrMo and Carbon with 50-50 mixing. The results show the danger of using pure geometric parameters such as “bond length” in describing metallic bonding in these materials.
11:45 AM Invited
Local Structure in Controlling Microstructure and Property of Lightweight High-entropy Alloys: Rui Feng1; Chuan Zhang2; Michael Gao3; Zongrui Pei3; Yan Chen4; Dong Ma4; Ke An4; Jonathan Poplawsky4; Fan Zhang2; Jeffery Hawk3; Peter Liaw1; 1University of Tennessee; 2Computherm, LLC; 3National Energy Technology Laboratory; 4Oak Ridge National Laboratory
The concept of high-entropy alloys (HEAs) opens up a new idea for developing advanced lightweight alloys for extreme-environment applications. Here, a series of lightweight HEAs are designed by the CALPHAD-based high-throughput computational method, targeting the high-temperature and cost-effective applications. These new alloys were investigated from the perspectives of structure, property, and deformation behavior, by the state-of-the-art neutron scattering and advanced microscopy. It is found that the local structure plays a critical role in controlling the morphologies of the constituent phases and the properties of these new lightweight HEAs. The present study provides helpful insights into tuning the properties of lightweight HEAs by tailoring their local structures.