High Entropy Materials: Concentrated Solid Solutions, Intermetallics, Ceramics, Functional Materials and Beyond II: Materials Discovery and Design II
Sponsored by: TMS Alloy Phases Committee, TMS Mechanical Behavior of Materials Committee
Program Organizers: Michael Gao, National Energy Technology Laboratory; Xingbo Liu, West Virginia University; Peter Liaw, University of Tennessee; Jian Luo, University of California, San Diego; Yiquan Wu, Alfred University; Yu Zhong, Worcester Polytechnic Institute; Mitra Taheri, Johns Hopkins University; Amy Clarke, Los Alamos National Laboratory
Monday 2:00 PM
October 18, 2021
Room: B131
Location: Greater Columbus Convention Center
Session Chair: Dan Thoma, University of Wisconsin-Madison; Keith Knipling, Naval Research Laboratory
2:00 PM Invited
Compositionally Complex Oxides: Synthesis, Characterization, Challenges, and Opportunities: Veerle Keppens1; 1University of Tennessee
High entropy oxides (HEOs), also referred to as multicomponent oxides or compositionally complex oxides (CCOs), have attracted attention due to the tunability of multiple cations on a single site. Since the introduction in 2015 of HEOs stabilized in the rocksalt phase, the high entropy oxide concept has been expanded to various structures, including fluorites, perovskites, and spinels. Here, we 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.
2:30 PM Invited
High-throughput Design and Processing of MPEAs Using Additive Manufacturing: Dan Thoma1; Michael Niezgoda1; Phalgun Nelaturu1; Zahabul Islam1; Michael Moorehead1; Adrien Couet1; 1University of Wisconsin-Madison
The large number of possible compositional variations with multi-principal-element alloys (MPEAs) requires bulk combinatorial processing methodologies to validate alloy design strategies. In this study, directed energy deposition (DED) is used for high-throughput additive manufacturing of bulk MPEAs, including refractory-based alloys and iron-based alloys. With four powder hoppers containing elemental powders, 25 bulk samples (1 x 1 x 1 cm), each with different compositions, can be processed within 4 hours. Actual vs. nominal compositions within 5% can be achieved. Test coupons exhibit less than 1% unmelted material and roughly 1% porosity. Moreover, owing to the high cooling rates in DED (~1000 K/s), secondary dendrite arm spacings are reduced by a factor of four as compared to arc-cast samples, permitting less homogenization times. Thermodynamic calculations and a new dimensionless number help predict process parameters, and examples of high-throughput characterization and property assessment of the 25 sample combinatorial plates will be introduced.
2:50 PM Invited
Refractory High Entropy Alloys with Balanced Properties Tailored for Service Conditions: Andrew Detor1; Scott Oppenheimer1; James Ruud1; Emily Cheng1; 1GE Research
Most commercial refractory alloys were designed with high temperature strength and manufacturability prioritized over oxidation resistance. This drives the need for complex and expensive coatings in aggressive service conditions. By lifting classic composition constraints through a high entropy alloying approach, it is possible to achieve improved balance-of-properties in refractory metals. Tailoring properties individually, as required for a specific application or as input for design trades, is also enabled. Here, we review recent work combining high throughput experimental screening, machine learning, and multi-objective optimization to explore a wide refractory alloy composition space. We demonstrate a materials informatics alloy selection process for extreme service conditions where oxidation resistance is prioritized alongside mechanical properties and manufacturability. Fundamental mechanisms driving competing properties are presented to clarify the compositional origin of tradeoffs. The general methods presented here can be applied to other applications and highlight the benefits of a materials informatics approach to alloy design.
3:10 PM Invited
Microstructures of Al2.7CrFeMnV, Al2.7CrFeTiV, and Al2.7CrMnTiV High-entropy Alloys: Patrick Callahan1; Keith Knipling1; 1Naval Research Laboratory
Three high-entropy alloys that have potential as lightweight structural materials have been studied using a combination of atom probe tomography (APT), electron backscatter diffraction (EBSD), transmission electron microscopy (TEM), and X-ray diffraction (XRD) as well as predictions from Thermo-Calc. The first alloy, Al2.7CrFeMnV, is a single-phase bcc, consistent with Thermo-Calc predictions. The two other alloys contain multiple phases. The second alloy, Al2.7CrFeTiV, is a solid solution bcc matrix with an Al-rich G-phase and a Laves phase rich in Ti and Cr. These were all present in the Thermo-Calc predictions. The third alloy, Al2.7CrMnTiV, is also bcc with an L10 phase, which was predicted by Thermo-Calc. Additionally, a nanoscale B2 phase in the form of coherent ~10 nm B2 cuboids is formed, resembling the γ-γ' microstructure of Ni-based superalloys but in a bcc system. In addition to the as-cast microstructures, we investigate aging the Al2.7CrMnTiV alloy to optimize the bcc/B2 microstructure.
3:30 PM Break
3:50 PM
Design of TWIP/TRIP Non-equimolar High-entropy Alloys: Xin Wang1; Rafael Tomás Rodríguez De Vecchis2; Chenyang Li3; Wei Chen3; Wei Xiong2; 1University of Pittsburgh; 2Physical Metallurgy and Materials Design Laboratory, Department of Mechanical Engineering and Materials Science, University of Pittsburgh, Pittsburgh, PA, 15261, USA; 3Department of Mechanical, Materials and Aerospace Engineering, Illinois Institute of Technology, Chicago, IL, 60616 USA
High-entropy alloys (HEAs) with transformation-induced plasticity/twinning-induced plasticity (TRIP/TWIP) attracted intense attention because of the excellent combination of strength and ductility. However, designing HEAs with TWIP/TRIP via the Edisonian approach is time and cost-consuming. Therefore, we demonstrated a new method utilizing the CALPHAD-based model and ab initio approach to predict the phase and deformation mechanism for a given composition. After screening ~100,000 CoxCryFezMnwNi100-x-y-x-w compositions, several compositions with different SFEs that cover the deformation mechanism from dislocation glide to TWIP and TRIP were selected and prepared. The designed alloys were systematically studied for the microstructure, mechanical property, and deformation mechanism. It was found that all the designed alloys have no intermetallic phases and show good ductility, and more than 80 % of the prepared alloys have TRIP/TWIP effects.
4:10 PM
Nanostructured Oxide-dispersion-strengthened CoCrFeMnNi High-entropy Alloys: Xiang Zhang1; Fei Wang1; Xing-Zhong Li1; Khalid Hattar2; Bai Cui1; 1University of Nebraska-Lincoln; 2Sandia National Laboratories
A nanostructured oxide-dispersion-strengthened (ODS) CoCrFeMnNi high-entropy alloy (HEA) has been synthesized by mechanical alloying process. The thermal stability, including the grain size and phase composition of the HEA matrix, as well as the particle size of oxide dispersions, were carefully investigated by electron microscopy characterizations after annealing at 900 oC. The limited grain growth may be attributed to Zener pinning of intergranular yttria dispersions that impede the grain boundary mobility. The hardness of nanostructured ODS CoCrFeMnNi HEA is 2.7 times higher than CoCrFeMnNi HEA without yttria dispersions. This research implies that the combination of ODS and HEA concepts may provide a new design strategy for the development of thermally stable nanostructured alloys for extreme environments.
4:30 PM Invited
Now On-Demand Only - Exploring the Feasible High Entropy Alloy Space: Raymundo Arroyave1; 1Texas A&M University
Over the past decades, the concept of "high entropy alloys" has become a source of inspiration for the field of metallurgy as we try to identify yet to be explored regions in the metal alloy space with properties that can potentially surpass those of alloys currently in use in a number of applications. The "high entropy" premise of much of the HEA program in the early years has given way to the argument that the HEA space is vast and therefore there are boundless opportunities for further discovery. While strictly speaking the HEA alloy+process space indeed is infinite, in this work we present some recent investigations that suggest that, while big, the feasible HEA space in any given sub-sector (e.g. FCC HEAs, RHEAs, etc) is severely constrained by typical alloy design considerations. Combining CALPHAD, physics-based models, machine learning, search/optimization algorithms we present a more nuanced view of the HEA space.
4:50 PM
Development of Low-cost High Entropy Alloys through Alloy Mixing: Karthikeyan Hariharan1; Katakam Sivaprasad1; 1National Institute of Technology,Tiruchirappalli
High entropy alloys (HEAs), have kindled interest among researchers for the past 15 years due to their unusually superior structural and functional properties. However, their application is limited by the fabrication cost as they are typically fabricated by vacuum melting methods of pure elements or by mechanical alloying using pure elemental powders. To overcome this issue, a new low-cost fabrication called “Alloy mixing” is proposed. In this method, it is proposed to melt different commercially available alloys to achieve HEA composition; this method would also permit the usage of scrap metals. A near-equiatomic HEA with a composition CrCuFeMnNi is fabricated using this new method.Our analysis shows that more than 40% reduction in cost is achieved while maintaining the same microstructure (verified through XRD and SEM) as that of the alloy fabricated by conventional methods;the cost can be further reduced with the usage of non-equiatomic HEAs.