High Entropy Alloys VIII: Alloy Development and Applications
Sponsored by: TMS Functional Materials Division, TMS Structural Materials Division, TMS: Alloy Phases Committee, TMS: Mechanical Behavior of Materials Committee
Program Organizers: Peter Liaw, University of Tennessee; Michael Gao, National Energy Technology Laboratory; E-Wen Huang, National Chiao Tung University; Srivatsan Tirumalai; Xie Xie, FCA US LLC; Gongyao Wang, Globus Medical
Wednesday 8:30 AM
February 26, 2020
Room: Mission Hills
Location: Marriott Marquis Hotel
Session Chair: Peter Liaw, University of Tennessee; Michael Bakas, Army Research Office
8:30 AM Invited
Multicomponent and High-entropy Cantor Alloys: Brian Cantor1; 1University of Bradford
Conventional alloying strategy is to select a main component for the primary property, with minor alloying additions for secondary properties. This has led to many successful materials, such as high-temperature Ni superalloys and corrosion-resistant stainless steels. We have, therefore, an enormous amount of knowledge about alloys based on one component, but little or no knowledge when several main components are mixed in near-equal proportions. Theoretical understanding is similarly restricted, based on the dilute solution approximation, ignoring non-linear correlations. We know much about alloys close to the corners and edges of multicomponent phase diagrams, with nothing known about alloys in the centre of the diagram.This paper describes alternative alloying strategies, discusses the number of possible materials, gives examples of multicomponent alloys, particularly fcc Cantor alloys based on Fe20Cr20Mn20Co20Ni20, emphasises the multitude of local environments, and discusses alloy microstructures and properties.
8:50 AM Invited
High Entropy Alloys for Magnetocaloric Effect Applications: Michael McHenry1; Alice Perrin1; 1Carnegie Mellon University
Magnetocaloric effect (MCE) materials offer efficient, environmentally friendly refrigeration. Rare earths metal (REs) compounds have large MCE near room temperature but their scarcity, high price and corrosion limit their use. Transition metal based high entropy alloys (HEAs) exhibit convenient tunability of Curie temperatures, Tc’s, use of inexpensive components and tunability of magnetic phase transformation breadth by distributing pair-wise exchange interactions on an fcc crystalline lattice. Intermetallics with less critical rare earths exhibit 1st order magnetostructural phase transitions where HEA arguments inspire compositional modifications. I will present Tc engineering in direct exchange coupled metals using the Bethe-Slater curve and Pauli exclusion principle constraints to explain composition- and pressure-dependence of Tc and Mossbauer spectra, where the average hyperfine field (and Tc) is proportional to the average pairwise exchange interaction. The P-dependence of Tc is interpreted for FeCoNiMnCu HEAs. Concepts for extending high entropy ideas to intermetallics in NaZn13-type cluster solids are presented.
9:10 AM
Designing Ductile Refractory High-entropy Alloys Guided by Natural Mixing: Shaolou Wei1; Sang Jun Kim2; Yongjie Zhang3; Goro Miyamoto3; Tadashi Furuhara3; Eun Soo Park2; Cemal Tasan1; 1Massachusetts Institute of Technology; 2Seoul National University; 3Tohoku University
Exhibiting the unique combination of high melting points and excellent softening resistance, refractory elements create interesting opportunities to design new high-entropy alloys (HEAs), aiming especially for superior high-temperature performances compared to conventional alloys. Yet, the search for optimal compositions have not yet been fully successful. In this regard, the intrinsic shortcomings of refractory metals such as brittleness at ambient temperature and catastrophic oxidation at elevated temperatures still remain as significant challenges. Here in this presentation, we will show that by making use of the natural thermodynamic mixing characteristics amongst refractory elements, novel body-centered cubic (BCC)-structured RHEAs can be developed. We will demonstrate two such RHEAs which exhibit unique specific strength-ductility synergy at room temperature and promising oxidation resistance at high-temperature. We will also systematically discuss the strengthening modules, the deformation micro-mechanisms, and the underlying RHEAs design principles.
9:30 AM Invited
Latest Developments in High Entropy Brasses & Bronzes: Kevin Laws1; Peter Nicholson1; Patrick Conway2; David Miskovic1; Lori Bassman3; Warren McKenzie4; 1University of New South Wales; 2Jönköping University; 3Harvey Mudd College; 4Advanced Alloy Holdings
The use of Brasses & Bronzes is subtly astounding, ranging from the keys in your pocket, zippers on your clothes, hinges, handle and lock mechanism of your front door, plumbing and electronic hardware, bearings, munitions and world coin currencies - arguably one of the most versatile alloy families known. Lead-containing brasses have been a key industry-enabling material due to their excellent castability, machinability, workability, low-friction properties and nobility. However, the brass industry is on the cusp of historic change. Widespread lead contamination in drinking water has escalated leaded brass to a global issue, with new legislation in the USA, Canada and Europe restricting lead-content in key brass grades, creating an immediate need to meet associated health and industry demands. The development of multi-component high entropy brasses has created new metallurgical avenues to address these problems. Here we report the most significant developments in this space over the last 5 years.
9:50 AM Invited
High-throughput Experiments for Structural Materials – A Current Status: Daniel Miracle1; 1Air Force Research Laboratory
High throughput experiments are essential to address the explosion in new alloy bases offered by high-entropy alloys (HEAs) and complex, concentrated alloys (CCAs). While a number of high throughput techniques are available for functional materials, the structural materials community has hardly advanced in the systematic use of this concept. In recent years, new ideas are being developed to address this gap. This presentation will review the status of the concept, development and application of high throughput techniques for structural materials. Key validations will be described and future work will be suggested.
10:10 AM Break
10:30 AM Invited
How High are the Entropies of High Entropy Alloys?: Kaituo Huo1; Qikai Li1; Mo Li2; 1University of Science and Technology Beijing; 2Georgia Institute of Technology; University of Science and Technology Beijing,
Entropy plays an important role in thermodynamics and kinetics of phase formation and structure stability, especially in the multicomponent alloy systems including the “high entropy” alloys. However, except for the entropy of mixing, other types of entropies in these systems remain less known. In this work, using a self-consistent model, we show the relative magnitudes of the entropies including the entropy of mixing and vibrational entropy. Our results indicate that the entropy of mixing in general does not contribute significantly to the alloy systems as compared with others. We will also discuss the contributions of each type of entropies to phase stability and phase formation.
10:50 AM
Decoding Early Candidacy of High Entropy Alloys for Nuclear Application using the Advanced Test Reactor through Predictive Methods: Geoffrey Beausoleil1; Jeffrey Aguiar1; Seongtae Kwon1; Eric Eyerman2; 1Idaho National Laboratory; 2California Nanotechnologies
High Entropy Alloys (HEAs) are identified candidates for nuclear applications owing to their superb mechanical and thermal properties. In line with evaluating their candidacy, a challenge remains in their validity as structural replacements for extreme environments. Each compositional graded specimen consists up to four different compositions spanning the fueled zone for non-prototypical neutron irradiation testing in the Advanced Test Reactor (ATR) at Idaho National Laboratory (INL). We have fabricated a set of four compositionally graded specimens using spark plasma sintering that include at least five of the following elements: Cr, C, Al, Zr, Mo, Nb, Ta, V, Ti, W, and Fe. In time for this meeting the role of temperature expected to play a role in-pile cladding chemical interactions (FCCI), mechanical interactions (FCMI), irradiation damage, creep, and resistance will be reported. The irradiated portion has a scheduled irradiation date in April 2020 and with post irradiation examination (PIE) to follow.
11:10 AM
Design of High-strength and Ductile High-entropy Steels: Zhangwei Wang1; Wenjun Lu1; Huan Zhao1; Dirk Ponge1; Dierk Raabe1; Zhiming Li1; 1Max-Planck-Institut für Eisenforschung
We have developed a new class of high-entropy steels (HESs) by taking the advantage of the previously proposed high-entropy alloy (HEA) design concept. These newly designed HESs contain five major components, in which Fe has the highest atomic fraction and the minimal content of each component is above 5 at. %. We investigated the nanoprecipitation behavior of carbides and B2 phases in these novel HESs by means of high resolution scanning transmission electron microscopy (STEM) and atom probe tomography (APT) at atomic scales. Upon uniaxial tensile testing, our HESs show excellent specific strength and ductility, outperforming both the previous HEAs and the advanced lightweight steels. We further systematically investigated the interactions between dislocations and second phases including carbides and B2 particles to explain the outstanding specific strength and ductility in the HESs. Our study thus provides a number of new insights for the design of high-performance novel structural materials.
11:30 AM Invited
High-Entropy Ceramics: Selected Recent Studies and Future Opportunities: Jian Luo1; 1University of California, San Diego
This talk will review our recent studies in fabricating and characterizing high-entropy ceramics. As examples, I will discuss several classes of high-entropy ceramics that first fabricated in our group at UCSD, including: high-entropy metal diborides as the first example of a new class of ultrahigh temperature ceramics [Scientific Reports 6:37946 (2016)], high-entropy perovskite oxides with two cationic sublattices [Scripta Mater. 142:116 (2018)], high-entropy fluorite-structured oxides with substantial oxygen vacancies [J. European Ceram. Soc. 38:3578 (2018)], and a high-entropy metal disilicide with a lower symmetry [Journal of Materiomics, https://doi.org/10.1016/j.jmat.2019.03.002 (2019)], as well as single-phase high-entropy intermetallic compounds (e.g., aluminides) that bridge high-entropy metals and ceramics [Science Bulletin 64:856 (2019)]. Furthermore, novel fabrication methods [e.g., reactive flash spark plasma sintering, Scripta Mater. 170:106 (2019)], microstructural controls, unique properties, and potential applications will also be discussed.
11:50 AM
Nanomolding Far and Close to Equilibrium: Naijia Liu1; Sungwoo Sohn1; Jan Schroers1; Arindam Raj1; Guannan Liu1; 1Yale University
Tremendous effort has been taken during the last two decades in the development of nano fabrication techniques for metals as they exhibit desirable functional properties. However, both bottom-up and top-down fabrication approaches are limited in some critical aspects such as material choice, geometry, and scalability. A highly versatile and widely used fabrication method is molding, which is generally associated with a soft state of a material. Nanomolding has been realized for polymers, gels, and some glasses, such as metallic glasses that soften at elevated temperatures, but not for crystalline metals that remain hard in their crystalline state. Recently, we discovered that nanomolding is possible with crystalline metals. Scaling considerations reveal that the underlying process is based on atomic diffusion down a pressure gradient. Most effective at ~0.5 Tm, such thermomechanical nanomolding (TMNM of crystalline metals) results in very high aspect ratio up to 1000 and nanowires as small as 5 nm in diameter.
12:10 PM Invited
Phenomenological Approach to Multi-principal-element Structural Materials: Joseph Poon1; Qi Jie1; John Scully1; Sean Agnew1; 1University of Virginia
The compositional and microstructural complexities of multi-principal-element alloys (MPEA) or compositional complex alloys (CCA) present great challenges for designing high-performance structural MPEA. The first challenge is to predict the compositional regions of different MPE alloys and composites with high reliability. We introduced several phase-diagram inspired parameters that were shown to enable clear 3D visualization of the solid solution regions. Encouraged by the finding, we employed machine learning to partition the formation regions of 600+ reported MPEA. The model achieved a single solid solution phase prediction rate greater than 80 %. Our phenomenological approach was validated by achieving near 80 % phase prediction rate for 40+ randomly selected compositions. The model is currently being utilized to design low-cost and low-density corrosion-resistant MPEA.