Advances in Multi-Principal Element Alloys II: Poster Session I
Sponsored by: TMS Structural Materials Division, TMS Functional Materials Division, TMS: Mechanical Behavior of Materials Committee, TMS: Alloy Phases Committee
Program Organizers: Peter Liaw, University of Tennessee; Michael Gao, National Energy Technology Laboratory; E-Wen Huang, National Yang Ming Chiao Tung University; Jennifer Carter, Case Western Reserve University; Srivatsan Tirumalai; Xie Xie, FCA US LLC; James Brechtl, Oak Ridge National Laboratory; Gongyao Wang, Globus Medical

Tuesday 5:30 PM
March 21, 2023
Room: Exhibit Hall G
Location: SDCC


J-4: A Dynamic Recrystallization-induced Heterostructuring Strategy via Hot Rolling in a Ferrous Multi-principal Element Alloy: Jungwan Lee1; Hyojin Park1; Sujung Son1; Jae Wung Bae2; Jinyou Kim3; Sung Kyu Kim3; Hyoung Seop Kim1; 1POSTECH; 2Pukyong National University; 3POSCO
    Microstructural heterogeneities of grain sizes, crystal structures, and/or elemental distribution are highly promising alloy design concepts for both high strength and ductility stemmed from their sufficient strain hardening capacity. There have been various strategies to induce the heterostructured microstructures, e.g., multi-phases, partial recrystallization, and inhomogeneous elemental distribution. Plenty of these studies required annealing process under certain conditions to obtain the desired microstructures. Here, we propose heterostructured ferrous multi-principal element alloys via hot rolling exhibiting superb combinations of strength and ductility. The heterogeneous microstructure is arised from dynamic recrystallization, which occurred during the hot rolling. With the heterogeneous microstructures as well as deformation-induced martensitic transformation at liquid nitrogen temperature, we rationalized the enhanced mechanical properties of the present hot rolled multi-principal element alloys in depth.

J-5: A Facile Strengthening Method by Co-doping Boron and Nitrogen in CoCrFeMnNi High-entropy Alloy : Sujung Son1; Jungwan Lee1; Peyman Asghari-Rad2; Gang Hee Gu1; Farahnaz Haftlang1; Hyoung Seop Kim1; 1Pohang University of Science and Technology; 2The Pennsylvania State University
    Doping the interstitial atoms on the high-entropy alloys (HEAs) has been studied by numerous metallurgists to utilize multiple strengthening mechanisms like significant solid solution strengthening, precipitation strengthening, and grain boundary segregation. The study on the HEAs with interstitial atoms has been limited to the HEAs with one type of interstitial atoms such as carbon, nitrogen, and boron. Meanwhile, the advantages of the co-doped high-entropy alloys with several interstitial atoms still remain a lack of understanding. In this presentation, we aimed to discuss the synergetic strengthening mechanisms of the B-N co-doped HEAs. The CoCrFeMnNi HEA with 0.8 at% of B and N was cast and subject to microstructure characterization and mechanical testing. The B-N co-doped HEA exhibits the enhanced yield strength of ~572.3 MPa and UTS of ~878.0 MPa with a ductility of ~49.8%. Co-doping the multiple interstitial atoms can be a feasible strengthening strategy for the diverse HEAs.

A High-Throughput Investigation of Composition-Microstructure Relationships in NbVZrMx Alloys: Katharine Padilla1; Zhaohan Zhang1; Rohan Mishra1; Katharine Flores1; 1Washington University in St. Louis
    Refractory complex concentrated alloys (RCCA) are promising materials for high-temperature structural applications due to their high strength and other favorable mechanical properties. Previous studies on NbVZr, which forms the basis for many RCCAs, have reported a multiphase microstructure comprised of BCC dendrites separated by two Laves phases, cubic C15 and hexagonal C14. Recent computational results indicate additions of Mo, Ta, and Ti can have varying stabilizing effects on the BCC phase, potentially form a single-phase solid solution alloy, based on composition and concentration. In this work, we apply a high-throughput synthesis technique to investigate and compare the compositional-microstructural relationships in NbVZrMox, NbVZrTax, and NbVZrTix. We use direct laser deposition to rapidly synthesize compositional libraries and apply a suite of characterization techniques to investigate the resulting microstructural evolution. Nanoindentation experiments are performed to investigate the relationship between composition and mechanical properties at temperatures up to 600 C.

J-6: A Micromechanical Investigation of the Orientation Dependent Plasticity of a MoNbTi Alloy: Glenn Balbus1; Satish Rao1; Oleg Senkov1; Eric Payton1; 1Air Force Research Laboratory, Materials and Manufacturing Directorate
    Refractory multi-principal element alloys (RMPEAs) are promising candidate materials for use in high temperature structural applications and other extreme environments. Recent experiments and simulations have highlighted the unusual deformation behavior of an equiatomic MoNbTi alloy, which exhibits slip on higher order planes and sluggish edge dislocation mobility. Here, we report the orientation dependent deformation behavior of MoNbTi utilizing micropillar compression and post-mortem transmission electron microscopy. Our results suggest that deformation in this system is largely mediated by kink-migration of screw dislocations, as evidenced by the absence of twinning-antitwinning asymmetry and the presence of long screw dislocations and significant dislocation debris in post-mortem observations. We also report an unusual orientation dependence of the yield strength, owing to the high stress required to facilitate slip on {110}-type planes. These results further demonstrate the unconventional plasticity in BCC RMPEAs, and highlight the importance of kink-migration of screw dislocations.

J-7: A Neural Network Model for High Entropy Alloy Design: Jaemin Wang1; Hyeonseok Kwon1; Hyoung Seop Kim1; Byeong-Joo Lee1; 1Pohang University of Science and Technology
    We suggest a novel and robust neural network model to relieve the burden of searching vast compositional space of high entropy alloys (HEAs) and confirm the superiority of the model by comparing its performance with several other models. The reasons for the high accuracy of the model are discussed around thermodynamic descriptors calculated by thermodynamic modeling and the effect of the convolution neural network in the model. Furthermore, we inverse-predicted using the model to design HEAs with good mechanical properties and conducted experimental verification of the designed HEAs to prove the validity of the model and alloy design method. The strengthening mechanism of the designed HEAs is further discussed by analyzing microstructure and calculating the lattice distortion effect. We calculated the lattice distortion effect by performing molecular dynamics simulation using a 2NN MEAM interatomic potential. This study demonstrates the reliability of the alloy design approach with the machine learning model.

A Statistical Study on Incipient Plasticity of Medium-/High-entropy Alloys: A-Hyun Jeon1; Yakai Zhao2; Zhe Gao1; Upadrasta Ramamurty2; Jae-il Jang1; 1Hanyang University; 2Nanyang Technological University
    The statistical nature of the transition from purely elastic to plastic deformation (i.e., “pop-in” behavior manifested as a sudden displacement excursion in load-displacement curve) in medium-/high-entropy alloys is explored. A series of nanoindentation tests with three spherical tips having different radii were performed on both face-centered-cubic and body-centered-cubic alloys in hydrogen-charged and uncharged state. The obtained results were systematically discussed in terms of the tip radius effect on the stochastic characteristics of the yielding behavior and its interplay with hydrogenation.

J-8: Abrupt Fluorite-pyrochlore and Pyrochlore-weberite Phase Transformations in Single-phase 20-component Ultrahigh-entropy Oxides: Keqi Song1; Dawei Zhang1; Jian Luo1; 1University of California, San Diego
    A new series of 20-component fluorite-based compositionally complex oxides (20CCFBOs) were synthesized. This series of 20CCFBOs undergo a fluorite-pyrochlore transition and a pyrochlore-weberite transition with one varying compositional variable x. Surprisingly, while the Gibbs phase rule allows the co-existence of up to 20 phases at thermodynamic equilibrium, 15 out of the 17 compositions possess single ultrahigh-entropy phases, the remaining 2 exhibit minor phases near the transition points. This observation may be explained by a high-entropy effect (prone to stabilize a single solid solution phase). Careful characterization suggests small, but abrupt, changes of order parameters (represented by the XRD superstructure peak intensity or peak splitting due to the change of symmetries) at both phase transformations and the possible existence of short-range order after the vanishing of long-range order. Understanding and controlling such phase transformations suggests a new route to manipulating ordering and properties of high-entropy and compositionally complex ceramics.

J-9: Activated Sintering of Ni-doped NbMoTaW Guided by a Computed Grain Boundary Diagram: Sashank Shivakumar1; Keqi Song1; Mingde Qin1; Chunyang Wang2; Tianjiao Lei2; Huolin Xin2; Tim Rupert2; Jian Luo1; 1University of California San Diego; 2University of California Irvine
    We have extended CALPHAD methods to grain boundaries (GBs) and computed a GB lambda diagram to forecast the formation of liquid-like interfacial phases (GB complexion) in Ni-doped NbMoTaW and related activated sintering. We subsequently confirmed the enhanced sintering of NbMoTaW with the addition of a minor amount of Ni within the solid solubility limit, which is attributed to the enhanced mass transport in the liquid-like interfacial phases formed at the sintering temperature. Careful STEM and SEM characterizations further suggested Ni-enriched interfacial phases likely formed at the high sintering temperature, but de-wetted the GBs during the slow furnace cooling, leaving weak Ni segregation at the GBs. Such activated sintering mechanism and GB lambda diagrams, which had been revealed and constructed for simpler binary refractory alloys like W-Ni in prior studies [Luo et al., APL 2005 & 2008], have been successfully extended to high-entropy alloys in this work.

J-10: An Investigation on Structure-property Correlation in TiVZrNb Light-weight High-entropy Alloy: Juree Jung1; Jinwoo Seok1; Jongtae Kim1; Songyi Kim1; Jiwoon Lee2; Gian Song2; Jaeyeol Jeon1; Junhee Han1; 1KITECH; 2Kongju National University
     Refractory high-entropy alloys (RHEA) with a bcc structure which is represented by the TiNbZrHfTa alloy show excellent mechanical properties not only at room temperature but also at elevated temperatures. However, RHEAs have relatively high density (ρ ≥ 9.0 g/cm3) and consist of costly metals, and therefore it is limited to be applied as a structural material. In this study, TiVZrNb light-weight HEAs (ρ ≤ 6.0 g/cm3) are developed. The alloys are designed to have single bcc structure and higher atomic size misfit(δ) than TiNbZrHfTa (δ = 4.9 %) alloy.The correlation between the structure and mechanical properties of the light-weight RHEAs is investigated in terms of a role of atomic size misfit in lattice distortion and solid solution strengthening. The local lattice distortion was analyzed using X-ray diffraction and Pair Distribution Function (PDF) method.

J-11: An Investigation on Transformation-induced-plasticity Mechanisms of Metastable Refractory Medium-entropy Alloys by Controlling Chemical Composition: Yunjong Jung1; Kangjin Lee1; Jiwoon Lee1; Junhee Han2; Ke An3; Chanho Lee4; Peter Liaw5; Gian Song1; 1Kongju National University; 2Korea Institute of Industrial Technology; 3Oak Ridge National Laboratory; 4Los Alamos National Laboratory; 5The University of Tennessee
     Refractory high-entropy alloys (RHEA) exhibit outstanding mechanical properties, such as high temperature strength, creep resistance, and thermal stability. Nevertheless, most of reported RHEAs are less compatible with industrial applications than FCC-HEAs due to limited ductility. For this reason, several alloy design strategies to tailor phase stability results in the occurrence of mechanical twinning or phase transformation during deformation have been attempted to improve the ductility of RHEA. In this study, we developed BCC-structured metastable refractory medium-entropy alloys (RMEAs) with the transformation-induced-plasticity (TRIP) effect by using Bo-Md diagram, which is known as a phase-stability diagram used for developing Ti alloys. This diagram allows for prediction of stability of BCC phase, which is associated with the martensitic phase transformation. To control the Bo-Md values, we designed Tix(ZrHf)yV0.1Nb0.1Ta0.1 medium-entropy alloys, and investigated the microstructure and deformation behavior, using scanning-electron microscope(SEM), X-ray diffraction(XRD), In-situ neutron diffraction(ND), and electron-backscatter diffraction(EBSD).

Atomistic Investigation of Elementary Dislocation Properties Influencing Mechanical Behaviour of Cr15Fe46Mn17Ni22 Alloy and Cr20Fe70Ni10 Alloy: Ayobami Daramola1; Anna Fraczkiewicz1; Ghiath Monnet2; Christophe Domain2; Gilles Adjanor2; 1Ecole des MINES SMS centre; 2DF Lab, Département Matériaux et Mécanique des Composants
    Molecular dynamics (MD) simulations were used to study elementary dislocation properties in a high entropy (HEA) model alloy in comparison with Austenitic Stainless Steel (ASS). Recently developed embedded-atom method (EAM) potentials were used to describe the atomic interactions in the alloys. Molecular Statics (MS) calculations were used to study the dislocation properties in terms of local stacking fault energy (SFE. MD was used to investigate the dissociation distance under applied shear stress as a function of temperature and strain rate. It was shown that higher critical stress is required to move dislocations in the HEA alloy compared with the ASS model alloy. The theoretical investigation of the dislocation mobility simulation results shows that a simple constitutive mobility law allows predicting dislocation velocity in both alloys over three orders of magnitude, covering the phonon drag regime and the thermally activated regime induced by dislocation unpinning from local complex configurations.

J-12: Atomistic Modeling of Physical Vapor Deposition and Melt-quenching of CoCrFeNiTix High Entropy Alloys: Aoyan Liang1; Andrea Hodge1; Diana Farkas2; Paulo Branicio1; 1University of Southern California; 2Virginia Tech
    There is a great need to understand composition-synthesis-structure relationships in compositionally complex high entropy alloys (HEA). Here, we use molecular dynamics simulations to study CoCrFeNiTix HEA stability in samples produced by physical vapor deposition and melting and quenching. Results reveal that samples with high Ti content have a strong tendency to amorphize, while samples with low Ti content form face-centered cubic structures regardless of the synthesis method. The simulation results are in good agreement with experimental results from physical vapor deposition and point to the effects of larger size elements in the complex alloy. Our work provides atomistic insights into the interconnections and differences between bulk and film HEA synthesis methods, as well as the relationship between HEA phase stability and composition.

J-106: Bridge Martensite Phase Transformation through Microbands for Superior Dynamic Mechanical Properties in a Metastable High-entropy Alloy: Aomin Huang1; 1Univerisity of California San Diego
    Multi-principal elements alloys with more than five components, namely high-entropy alloys (HEAs) have been extensively studied due to their excellent mechanical properties as promising structural materials. As novel metallic alloys, excellent performances have been reported in recent studies. However, most emphasis has been placed to study their mechanical properties subjected to low strain-rate which leads to insufficient understanding of their properties at high strain-rate. In the present study, varying strain rates and temperatures of compression tests are performed on split-Hopkinson pressure bar (SHPB) system to establish their microstructure evolution and deformation mechanisms. We report on a new strategy to improve the dynamic mechanical properties of coarse-grained HEAs by introducing microbands as a bridge to initiate the stress-induced martensitic transformation (SIMT). This alloy exhibited yield stress over 1.2 GPa with good deformability under high-strain-rate loading.

J-14: Combinatorial Study of Rhenium Additions on the Non-Equiatomic VNbMoTaW System: Taohid Bin Nur Tuhser1; Thomas Balk1; 1University of Kentucky
    The superior strength of refractory multi-principal element alloys (RMPEAs) at elevated temperature is often paired with poor room temperature ductility. Re addition has been adopted successfully to enhance ductility in traditional W- and Mo-based refractory alloys. In this study, we investigated the effect of Re additions on the structural and mechanical properties of VNbMoTaW system using a combinatorial screening approach. A 2D gradient compositional film of VNbMoTaWRe was deposited by magnetron sputtering. The alloy phase map was constructed using EDS and XRD. Nanoindentation was performed at different strain rates to compare hardness, elastic modulus, and strain rate sensitivity. The tensile properties of selected compositions were studied by in situ fragmentation testing. Configurations with enhanced ductility were suggested based on the crack onset strain and fracture morphology. Finally, bulk samples of screened alloys were prepared, and corresponding bulk mechanical properties were compared with the thin-film counterparts.

J-15: Combinatorial Thin Film and Bulk Alloy Approach to Identify Non-equiatomic Compositions in MnFeCoNiCu System with Superior Phase Stability and Mechanical Properties: Tibra Das Gupta1; Thomas Balk1; 1University of Kentucky
    In this study, using a combinatorial thin film approach, we searched for alloy compositions in the MnFeCoNiCu system that exhibit superior mechanical properties and phase stability. Thin films with 2D composition gradient were fabricated using magnetron sputtering, and mechanical properties were measured across the gradient by nanoindentation. Certain alloys in the non-equiatomic system exhibited improved mechanical properties in comparison to the equiatomic counterpart. Bulk specimens of candidate alloys from the non-equiatomic system were prepared by arc melting, and tension tests were performed with a custom-built micro-specimen testing system. High-temperature mechanical testing was also conducted using a Gleeble thermo-mechanical simulator.

J-16: Comparison of Select High Entropy Alloys as Binders for Cemented Carbide: Jannette Chorney1; Jerome Downey1; K.V. Sudhakar1; 1Montana Technological University
    Select high entropy alloys (HEAs) have been investigated as potential binders in cemented tungsten carbide. The HEA binders were prepared by powder metallurgy and fusion techniques. Process temperatures were determined by differential scanning calorimetry/thermal gravimetric analysis (DSC/TGA). The HEAs and the cemented carbide produced with HEA binders were characterized using Differential Scanning Calorimetry/Thermal Gravimetric Analysis and Scanning Electron Microscopy (SEM) imaging and Energy Dispersive Spectrometry (EDS), and Vickers hardness testing. A comparative analysis of the properties of the fused melt HEAs and the corresponding cemented carbides is presented.

J-17: Comparison of Tensile and Compression Properties of Refractory High Entropy Alloys Developed by Natural Mixing Guided Design: Jae Kwon Kim1; Sang Jun Kim1; Eun Soo Park1; Taeyeop Kim2; Dongwoo Lee2; Hyun Gi Min1; 1Seoul National University; 2Sungkyunkwan University
    Currently, as the demand for performance and efficiency improvement of high-temperature structural materials, BCC refractory high entropy alloy (RHEAs) can potentially be suitable for this demand. But it is difficult to systematic alloy design because RHEAs are composed of a large number of major elements in a similar fraction that cannot select a specific major element. Moreover, although safety-critical structural materials require sufficient strength and ductility in tension, the mechanical properties of RHEA have invariably been investigated in compression. In this study, we try to solve the above two limitations by evaluating of tensile properties of the selected RHEAs via a unique alloy design that is a method of selecting by nature upon solidification on a multi-component alloy. Finally, we clarify the difference between the two deformation modes depending on microstructural imperfections by comparing the tensile and compressive properties. Our study will bring RHEAs closer to the standard of safety-critical alloy.

J-18: Crystal Plasticity Modeling and Machine Learning for High-Strength, High-Temperature Alloys: Stephanie Taylor1; Jaime Marian1; Amartya Banerjee1; 1University of California Los Angeles
    Materials that can withstand extremely high temperature environments are desirable to identify for application in the next generation of energy technologies. Such environments are difficult to study experimentally, so computational techniques find a relevant niche here. To this end, we have pursued a novel computational approach by coupling crystal plasticity (CP) simulations and machine learning (ML) to explore unique multi-principle metal alloy compositions capable of high temperature strength. Results from these CP simulations and implemented ML algorithms are presented. Special focus is paid to discussing the properties that are well-captured by the combination of these techniques.

J-102: Crystallographic and Compositional Evolution during Isothermal Annealing of Refractory High Entropy Alloys: Insights into High Temperature Phase Stability: Sriswaroop Dasari1; Abhishek Sharma1; Rajarshi Banerjee1; Vishal Soni1; 1University of North Texas
    The microstructure similar to Ni-base superalloys can be achieved in refractory high entropy alloys (RHEAs) containing Al, albeit with a combination of BCC and B2 phases. Since the ordered B2 phase is based on BCC parent matrix, distinguishing these two phases can be rather challenging. Additionally, there is a tendency for transformation of ordered B2 phase into more complex ordered-omega type phases that are usually deleterious to mechanical properties. Three types of ordered omega phases can form from a parent B2 phase and these transformations were studied using candidate RHEAs, Al0.5Mo0.5NbTa0.5TiZr, Al0.5NbTa0.8Ti1.5V0.2Zr and AlNb1.5Ta0.5Ti3Zr4 alloys. The results from advanced microscopy techniques including correlative TEM-APT show that a metastable two-phase BCC+B2 microstructure formed in early stages of decomposition later transforms into a three-phase BCC+B2+ordered omega microstructure. The effect of such transformation on mechanical properties will also be discussed.

J-19: Data-driven Search and Selection of Ti-containing Multi-principal Element Alloys for Aeroengine Parts: Tanjore Jayaraman1; Ramachandra Canumalla2; 1University of Michigan-Dearborn; 2Weldaloy Specialty Forgings
    Rapidly growing interests in Ti-containing multi-principal element alloys (MPEA), due to their distinct combination of the room- and elevated-temperature mechanical properties and corrosion resistance for a wide range of potential applications, motivated us to analyze the literature data for the Ti-containing MPEAs to unearth the composition-processing-microstructure-property relationships for aeroengine applications. We applied advanced statistical analysis—including principal component analysis (PCA) and hierarchical clustering (HC)—and multiple-attribute decision making (MADM) synergistically to hear the voice of the data. The ranks assigned by several MADMs, including ARAS (additive ratio assessment), ROVM (range of value method), and MEW (multiplicative exponent weighing), were consistent. However, the ranks of the alloys varied by varying the relative weights of various properties, which revealed several MPEAs’ potential to substitute a range of aeroengine parts. The analyses suggest potential replacement substitutes and provide possible directions for the design and improvement of titanium-containing MPEAs.

J-20: Design of Ductile Low-Activation Bcc Multi-principal Element Alloys: Heng Jiang1; Ming Wang1; MingXin Huang1; 1The University of Hong Kong
    Low-activation body-centered cubic (bcc) multi-principal element alloys (MPEAs) are promising structural materials for nuclear power plants to ensure good radiation resistance and safe operation in service. Accordingly, a novel bcc MPEAs family consisting of only low-activation elements was proposed in this study. High-throughput experiments and machine learning were combined to explore an empirical criterion for rapidly discovering the relationship between composition and compression ductility. The average concentration of atomic mass () emerged as an effective indicator to identify the candidates with desirable ductility. Leveraging this criterion, an alloy with a satisfactory combination of ultimate tensile strength ( ~832 MPa) and fracture strain ( ~17.2%) at the typical service temperatures in terms of nuclear structural materials was determined. It kept bcc single-phase while deforming. The effects of tensile temperature and strain rate on the mechanical property were also discussed, respectively. Our results are a step forward in the exploration and design of high-performance low-activation bcc MPEAs in the field of nuclear application.

J-21: Design of MoWTaTiZr Refractory Multi-principal Element Alloys for High-temperature Applications: Gaoyuan Ouyang1; Prashant Singh1; Jun Cui2; Matthew Kramer1; Oleg Senkov3; Daniel Miracle3; Duane Johnson1; 1Ames Laboratory; 2Iowa State University; 3Air Force Research Laboratory
    The high specific strength at elevated temperatures exhibited by Refractory Multi-Principal Element Alloys (RMPEA) makes them suitable for a number of aerospace and engineering applications. However, many reported RMPEAs that retain their high strength above 1000°C are brittle, and their creep properties are mostly unknown. In the quintenary system Mo-W-Ta-Ti-Zr, we have identified several new molybdenum-rich compositions that experimentally show three times more ductility than the equiatomic NbTaMoW RMPEA at room temperature, two times stronger than TZM at 1300 °C, and ten times more creep resistant than TZM and nickel-based superalloy at 1000 °C. We will discuss our computational approach to identify the appropriate phase space, rapid bulk-alloy synthesis and characterization, down-selection criteria for selecting the alloys, and the application of small-punch test to evaluate tensile and creep properties above 1000°C for the newly developed alloys.

J-22: Design of Novel AlCoCrNbNi Eutectic High Entropy Alloy with Adequate Strength, Ductility, and Oxidation Resistance: Lavanya Raman1; Shweta Sharma1; Gagan Goyal1; Saurabh Singh1; Yu Zhang1; Na Liu1; Amin Nozariasbmarz1; Bed Poudel1; Ravi Sankar Kottada2; Wenjie Li1; Shashank Priya1; 1Pennsylvania State University; 2Indian Institute of Technology Madras
    Recently, eutectic high entropy alloys (EHEAs) consisting of hard and soft phases have gained great attention due to the synergy of high strength and ductility for various industrial applications. In this study, we have developed Al-Co-Cr-Nb-Ni eutectic alloy system, where the Al/Nb ratio is tuned to tailor the eutectic microstructure. The as-cast EHEAs composed of a soft fcc matrix with a hard Laves phase and B2 phases, displaying an optimum combination of strength and ductility. A two phase to triple phase eutectic microstructure is obtained at high Al/Nb ratio. Furthermore, an excellent oxidation resistance was observed with high Al/Nb ratio at 1173 K for 100 h. This new alloy design strategy can be adapted to other HEA families with simultaneous high strength and ductility along with better oxidation resistance.

J-103: Development and Application of WC-based Cemented Carbide Bonded with Co Based Multi-component Alloy Binder: Jinwoo Seok1; Jun-Woo Song1; Juree Jung1; Jong Tae Kim1; SongYi Kim1; Hyoseop Kim1; Moon-Jo Kim1; Seul-Ki Han1; Junhee Han1; 1KITECH
    Cemented carbide composed of Tungsten Carbide(WC) and cobalt metal binder is a representative material for cutting tools because of its superior mechanical properties. There are strong demands for reduction or replacement of Cobalt in different industries due to the recent price hike and supply instability. Therefore, Co-based multi-component alloys are developed as alternative binder in order to reduce the content of Co and improve the mechanical properties of cemented carbide. A mixture of WC and alloy binder was sintered by Spark Plasma Sintering(SPS) at vacuum atmosphere after high-energy ball milling. Microstructures and mechanical properties are analyzed by X-ray diffraction, Scanning-Electron microscopy, Energy-Dispersive Spectroscope and Vickers Hardness tester(30kgf). The WC-CoNiX cemented carbides showed excellent mechanical properties compared to the conventional WC-CO and this suggests that the alternative alloy binders developed in this study have applicability to a new type of cemented carbide for cutting tool materials.

J-23: Accelerated Development of Refractory Multi-principal Element Alloys via Machine Learning: Carolina Frey1; Anthony Botros1; Chris Borg2; James Saal2; Bryce Meredig2; Noah Phillips3; Tresa Pollock1; 1University of California Santa Barbara; 2Citrine Informatics; 3ATI
    Refractory Multi-principal Element Alloys present an opportunity for new high temperature alloys that can operate at temperatures above 1200°C. However, balancing high temperature strength and room ductility remains a challenge. Machine learning methods have the potential to reduce the number of needed experiments and more efficiently discover interesting materials demonstrating necessary properties. This presentation will discuss the use of random forest machine learning algorithms in concert with CALPHAD to guide sequential alloy design. Predictive models for room temperature, 1000°C and 1200°C yield strengths are presented. High performing alloys were identified in the Hf-Mo-Nb-Ta-Ti system. Compressive mechanical properties of as-cast alloys at room and high temperature in this system are reported, and the effect of iteration on model fidelity is discussed. CALPHAD predictions are evaluated via annealing experiments at 700°C-800°C. The effect of oxygen content on strength and phase formation are also reported. Other high performing alloy systems are discussed.

J-24: Development of Refractory High Entropy Alloys via Natural Mixing Guided Design: Jae Kwon Kim1; Sang Jun Kim1; Taeyeop Kim2; Dongwoo Lee2; Eun Soo Park1; Hyun Gi Min1; 1Seoul National University; 2Sungkyunkwan University
     BCC refractory high-entropy alloys (RHEAs) made of group 4-6 refractory transition elements have superior high-temperature strength and structural stability. However, a systematic alloy design method has not been established. Meanwhile recently, a Unique alloy design method has been reported for extracting RHEA from solidified microstructure obtained from a multi-component alloy. In order to expand this design, it is essential to check the solidification behavior depending on the multi-component alloy composition. but solidification sequence analysis has not been clearly identified yet. In our study, we investigated the solidification sequence of 9 and 8-component alloys and tried to understand the relationship between solidification behavior differences depending on the composition of the multi-component alloy and the resulting RHEAs composition. Through this study, we can find a total of 20 RHEAs alloys. Our research has presented a new paradigm in the design of alloys for RHEAs by extending the method of designing alloys selected by nature.

J-25: DFT Investigation of FeNiCoCrMnAl and FeNiCoCrPdAl High Entropy Alloys: Fully Disordered versus Partially Disordered: Nguyen-Dung Tran1; Ying Chen1; 1Tohoku University
    High entropy alloy (HEA) represents a novel concept of alloy system in which multi-principle elements are mixed together in near-equiatomic proportions, resulting in some superior properties which attracts many researches recently. In this study, we investigate two 6-element high entropy alloys systems, e.g FeNiCoCrMnAl and FeNiCoCrPdAl in fcc and bcc single-phase solid solution, based on first-principle calculation and special quasi-random structure (SQS) model. The electronic structures and phase stability were calculated, with paying attention on the effect of Al content. Within equiatomic composition, we also consider the partially disordered L12, L10, and B2 structures in parallel with fully disordered ones, to investigate the effect of partial disordering on relative phase stability, considering the function of configurational mixing entropy by varying the concentration of constituents in sublattice sites, and the pair interaction preference among elements. Some partial disordering structures are found to be more stable than fully disordered ones.

Cancelled
Diffusion (Atomic Mobility) Databases for High-entropy Alloys: Wei Zhong1; Ji-Cheng Zhao1; 1University of Maryland
    Simple yet robust models for diffusion coefficients (atomic mobilities) – the Z-Z-Z binary model and Z-Z-ternary model – have recently been developed for binary and ternary metallic solid solutions. These models substantially simplify the extension to multicomponent systems with much reduced number of fitting parameters compared to the conventional CALPHAD atomic mobility assessment practice. Systematic assessments of the diffusion coefficients in the subsystems (especially binaries) of fcc Al-Co-Cr-Cu-Fe-Mn-Ni and bcc Cr-Hf-Mo-Nb-Ta-Ti-V-W-Zr high-entropy alloys (HEAs) have been carried out using these models to establish reliable diffusion (atomic mobility) databases for the common fcc-based and bcc-based HEAs. The ability of such databases in describing the diffusion behaviors in multicomponent HEAs was tested by comparing the model results with experimentally measured diffusion coefficients of HEAs reported in the literature over the past several years. These databases will be very useful for modeling the kinetic processes such as precipitation and creep deformation in HEAs.

Cancelled
Directional Solidification of the Medium-entropy Alloys from Al-Cr-Fe-Ni System: Oleg Stryzhyboroda1; Ulrike Hecht1; Victor Witusiewicz1; 1Access e.V.
     Recently materials research turned to high- and medium-entropy alloys aiming at exploring new materials design options. Besides microstructure-property relationships, microstructure formation is a key issue. Among the various phase transformations, solidification has received little attention. Particularly interesting are mushy zone characteristics including the nature of the primary phase, the microsegregation and sequence of secondary phase formation inside the mushy zone. Bridgman unidirectional solidification was selected as an experimental method to investigate these characteristics. We performed Bridgman experiments with the medium entropy alloy AlCrFe2Ni2 and quantitatively analyzed microsegregation by EDS using grid statistical analysis together with the weighted interval rank sorting (WIRS) procedure. The microsegregation data shed new light on phase equilibria with participation of the liquid phase. We used the data along with other experimental data from isothermal ageing for developing an optimized CALPHAD database for the Al-Cr-Fe-Ni alloy system. The experimental results and computed phase equilibria will be presented.

J-26: Ductility at Room Temperature of BCC-RHEAs: Jin Wang1; Nicolas Peter1; Ruth Schwaiger1; 1Forschungszentrum Juelich Gmbh
    Body-centered-cubic (BCC) high-entropy alloys (HEAs) revealed improved high temperature resistance compared to face-centered-cubic HEAs and superalloys [Lee2021]. The brittleness of most refractory HEAs (RHEAs) at room temperature, however, limits their application. As an example, the equimolar NbMoCrTiAl alloy was reported having little ductility up to 600 °C [Chen2016]. One exception of BCC-RHEAs is the equimolar TiNbHfZrTi alloy, which shows notable ductility at room temperature [Senkov2015, Dirras2016]. To understand the influence of microstructure on their deformation behaviors under different loading conditions, a series of micro-mechanical experiments including nanoindentation, micro-cantilever and micro-pillar tests were conducted on both alloys. The NbMoCrTiAl alloy, unexpectedly, exhibits significant ductility in the micro-mechanical experiments, especially in the single-crystalline micro-pillar compression tests along the <100> and <110> crystal orientations. Remarkable deformation features, such as slip bands and kink bands, were observed, and the alternating slip and kink processes support the strain achieved >35% comparable to Senkov alloy.

J-27: Dynamic Precipitate Transformation in Ultrastrong and Ductile Maraging Medium-entropy Alloy: Hyun Chung1; Won Seok Choi2; Hosun Jun2; Pyuck-Pa Choi2; Heung Nam Han3; Won-Seok Ko4; Seok Su Sohn1; 1Korea University; 2Korea Advanced Institute of Science and Technology; 3Seoul National University; 4Inha University
    High strength and ductility are structural materials’ basic and indispensable features under extreme conditions. Over the past two decades, numerous investigations for high-/medium-entropy alloys have been made due to their outstanding mechanical properties and rapidly increased. However, design strategies for precipitate-strengthened or martensitic MEA/HEA are not well established. Here, we investigated FeCo-based precipitate-strengthened martensitic MEA with ultrahigh strength with sufficient ductility overcoming the strength-ductility trade-off relationship based on designing metastable precipitates. The so-called maraging process introduces two types of ordered-structure precipitate with narrow stability gap; one within the matrix as an efficient dislocation barrier and a dislocation glide media; another along the grain boundary, which goes through dynamic phase transformation under load. These effects result in doubled strength and ductility, thus suggesting an alloy design strategy for further development of ultra-high strength materials.

J-28: Effect of Composition and Dose Rate on the Irradiation Behavior of Ni-based MPEAs: Anshul Kamboj1; Emmanuelle Marquis1; 1University of Michigan, Ann Arbor
    Nickel-based multi-principal element alloys (MPEAs) offer promises for nuclear application due to their superior mechanical properties. In addition, as compared to the less concentrated alloys, MPEAs such as CrFeNiCo, CrFeNiMn, CrFeNiCoMn, and CrFeNiCoPd have shown excellent phase stability, high swelling resistance, delayed energy dissipation, and suppressed damage evolution under high dose rate environment (>10^-3 dpa/s). However, these high dose rates are not representative of actual nuclear reactor environment, therefore, understanding the possible effects of dose rates on the irradiation behavior of MPEAs is needed. We investigated the microstructural response of a series of alloys of increasing compositional complexity that were ion irradiated at 10^-4 dpa/s and 10^-5 dpa/s. Transmission electron microscopy and atom probe tomography revealed phase decomposition in CrFeNiMn23 and CrFeNiCoPd MPEAs. In addition, the effect of composition on dislocation loops and cavity swelling was found to significantly decrease with decreasing dose rates.

J-29: Effect of the BCC Phase on Microstructures and Mechanical Properties of the FeCrNi Equiatomic Alloy: Jin-Seob Kim1; Jin-Kyung Kim1; 1Hanyang University
    The FeCrNi equiatomic medium entropy alloy has received attention as a cost-effective class of high/medium entropy alloys. The material shows the single FCC for the annealing temperatures higher than 900 ℃ while the Cr-rich BCC phase is formed in the FCC matrix for the annealing temperatures lower than 900 ℃. The BCC phase shows characteristic equiaxed and rod morphology depending upon annealing temperatures. For the annealing temperatures ranging from 700-900 ℃, a mixed equiaxed and rod-shaped BCC phase is present. Thus, we focus on microstructure evolution and mechanical properties of the materials with increasing annealing time at 800 ℃. The BCC phase fraction saturates in the annealing condition of 5 h at 800 ℃. Further, recrystallization is sluggish due to the presence of the BCC phase in the FCC matrix. We discuss the detailed microstructure-mechanical properties relationship of the investigated materials.

J-30: Effects of Oxygen Interstitials on Phase Stability and Phase Evolution in the HfNbTaTiZr RMPE Alloy: Leah Mills1; Ravit Silverstein1; Noah Philips2; Daniel Gianola1; Tresa Pollock1; 1University of California-Santa Barbara; 2ATI Specialty Alloys and Components
    Interstitials in BCC alloys can have a major influence on phase constitution, dislocation mobility and consequently mechanical properties. However the mechanisms by which interstitials influence properties are not fully understood in refractory multi-principal element alloys (RMPEAs). The effects of dilute amounts of oxygen on phase transformation mechanisms and tensile properties are investigated in the HfNbTaTiZr (Senkov) alloy. When subjected to tensile testing at 800°C in vacuum, the alloy exhibits reduced tensile ductility. Annealing at 800°C/100h in gettered Ar followed by nanoindentation reveals soft BCC grain boundary precipitates that enable intergranular failure. Annealing in a controlled oxygen environment at 900°C induces phase separation into a BCC phase and nm-scale O' phase. The O' phase is an intermediate phase to HCP, following the Burgers transformation path. With longer oxygen exposures, O' is consumed by BCC and HCP colonies. The implications for control of constituent phases and properties in RMPEAs will be discussed.

J-31: Effects of Potential Energy Statistics on Deformation Behavior in Concentrated Solid Solutions: Amir Shirsalimian1; Ritesh Jagatramka2; Junaid Ahmed2; Matthew Daly2; 1University of Illinois Chicago; 2University of Illinois-Chicago
    Recent studies of concentrated solid solutions, which include multi-principal element and high entropy alloys, have underscored the role of varied solute interactions in the driving a wide variety of mesoscale properties. These solute interactions emerge as fluctuations in potential energy that arise from local variations in the chemical environment. In this work, we overview some recent progress in connecting the topological statistics of concentrated solid solutions with the emergent mesoscale plasticity mechanisms. This discussion will begin with a theoretical examination of the fluctuations in defect energies that emerge in concentrated mixtures, followed by a computational investigation of changes in deformation twinning mechanisms in systems with variable defect energies. Extensions of this effort towards quantifying statistics in vacancy formation and migration energies, and other defects associated with high temperature deformation will be overviewed.

Cancelled
J-32: Enabling High-strength Refractory Complex, Concentrated Alloys via Multi-fidelity Experiments and Simulations: Michael Titus1; Austin Hernandez1; Sharmila Karumuri1; Saswat Mishra1; Zachary McClure1; Kenneth Sandhage1; Ilias Bilionis1; Alejandro Strachan1; 1Purdue University
    Refractory complex, concentrated alloys (RCCAs) can be defined as refractory-based alloys that comprise four or more elements with near equimolar compositions. Some of these alloys have recently been shown to exhibit remarkable high temperature strength, exceeding that of Ni-based alloys. In this work, we will present a new machine learning for accelerated materials discovery (ML-AMD) framework that utilizes multi-fidelity and multi-cost experiments and physics-based modeling to discover high strength, single phase RCCAs containing Al. New semi-high-throughput methods for characterizing strength of alloys will be presented, and methods for implementing high-throughput simulations into the ML-AMD framework will be expounded. This work discovered five new alloys exceeding any previously reported literature alloys with comparable microstructure features. New promising alloys will be identified, and strategies from improving strength and accelerating discovery of RCCAs will be discussed.

J-33: Enhanced Mechanical Properties of Ti-rich Medium Entropy Alloys via Phase Diagram Engineering: Wen-Chi Yang1; Ping-Yuan Deng1; Hsin-Jay Wu1; 1National Yang Ming Chiao Tung University
    Medium entropy alloys (MEAs) have gained attention for their excellent mechanical properties, such as high strength and relatively high ductility that could even outperform the well-established and commercially-use Ti-6Al-4V. In particular, the MEAs comprising elements of Al and Ti attract enormous attention due to their lightweight feature compared to well-developed CoCrNi MEAs. This study constructs the phase diagrams of Ti-Al-Cr-V by experiments, such that the ordered B2 phase can be clearly distinguished from the disordered BCC phase via synchrotron x-ray measurements. Alongside the phase diagram determination, the microstructural evaluation and structural transformation for MEAs were captured. By associating the metallographic information with physical properties, promising MEAs with enhanced mechanical properties and desired transport properties can be located via the phase diagram engineering.

Evolution of Hierarchical Nanotwins in the Annealed Mn-free FeCoNiCr High-entropy Alloy Subjected to Ex-situ Tensile Deformation at a Cryogenic Temperature: Tsai-Fu Chung1; Ching-Wen Yeh1; Chih-Yuan Chen2; Chien-Nan Hsiao3; Cheng-Si Tsao4; Jer-Ren Yang5; 1National Yang Ming Chiao Tung University; 2National Taipei University of Technology; 3Taiwan Instrument Research Institute; 4Institute of Nuclear Energy Research; 5National Taiwan University
    In this work, the microstructures of annealed Mn-free Fe27Co24Ni23Cr26 high-entropy alloy were examined at different stages of the tensile deformation at -150 °C. First, boundaries of the primary and secondary deformation nanotwins can confine the movement of dislocations. In the matrix of grain, the intersected region of the deformation nanotwins easily intrigues the formation of tertiary deformation nanotwins. As the flow stress increases, the pre-existing annealing-nanotwins were first refined by the primary deformation nanotwins and further divided by the secondary deformation nanotwins, bringing about dynamic grain refinement. At the ultimate strength stage, the intersected deformation nanotwins within the matrix of annealing-nanotwins have been found. Moreover, the matrix of secondary deformation nanotwins is significantly refined by tertiary deformation nanotwins. It is suggested that twinning occurs first in the matrices of grains, enhancing the initial work-hardening; subsequent the hierarchical twinning takes place in pre-existing annealing-nanotwins, thereby promoting further straining.

J-109: Fabrication of AlCoCrFeNi High Entropy Alloys via Binder Jetting and Direct Energy Deposition: Characterization, Microstructural Modification, and Analysis: Olujide Oyerinde1; Justin Almeida1; Ioannis Mastorakos1; Philip Yuya1; Ajit Achuthan1; 1Clarkson University
    Additively manufactured high-entropy alloys (HEAs) are in the early stage. More studies are required on how their compositions, processing routes, and microstructural evolutions influence HEAs (mechanical) properties for various fields of applications. In this study, the equiatomic AlCoCrFeNi high entropy alloy was fabricated via two additive manufacturing routes: binder jetting (3DBJ) and direct energy deposition (DED). The response of the samples to isothermal heat treatment was investigated and compared with the as-printed samples. Their microstructural evolutions were studied with scanning electron microscopy, energy dispersive spectroscopy, and X-ray diffractometer. Nanoindentation was used to characterize their mechanical properties. The results show that the 3DBJ and DED samples respond differently, as diffusion mechanisms like grain boundary precipitation, precipitate-free zones, and widmanstatten structure were more observable in the 3DBJ samples. The 3DBJ samples also exhibit higher values of mechanical properties. This insight about AlCoCrFeNi will benefit the tools, automobile, structures, and aerospace industries.

J-34: Grain Boundary Segregation and Solute Drag in Multicomponent Alloys: Milad Taghizadeh1; Malek Alkayyali1; Fadi Abdeljawad1; 1Clemson University
    Controlling grain boundary (GB) dynamics in polycrystalline materials is of great significance since it can lead to the fine-tuning of the mechanical and physical properties through microstructure control. Recently, GB segregation emerged as a technique to mitigate GB migration and stabilize nanocrystalline grain microstructures. However, GB segregation and dynamic solute drag remain poorly understood in multi-component alloys. Herein, we present a model of GB solute drag that accounts for the interactions of various elemental species with migrating GBs in multi-component alloys and captures complex solute-solute interactions in such systems. Ternary alloys are employed here as a canonical demonstration of multi-component effects. Parametric studies are performed to reveal regimes in alloy design space where solute drag effect is maximized. Several segregation effects are demonstrated including competitive and synergistic segregation and induced de-segregation. Our modeling approach provides avenues to account for solute-defect interactions in alloy design and discovery efforts.

J-35: Grain Boundary Segregation Effects in Multi-Principal Element Alloys: Sarah Paguaga1; Sarah Hunt1; Joshua Arrington1; Fadi Abdeljawad1; 1Clemson University
    Multi-Principal Element Alloys (MPEAs) have been the subject of active research for their unique combinations of properties. However, most existing research focuses on bulk properties of MPEAs and solute-defect interactions in these systems remain unexplored. Of particular interest is the interaction of elemental species with grain boundaries (GBs), as these affect many microstructural evolution processes. In this study, we leverage atomistic simulations to construct atomistic bicrystals with a series of [001] asymmetric GBs. The AlFeNiCrCo and HfNbTaTiZr systems are used as model MPEAs with FCC and BCC crystal structures, respectively. Then, hybrid Monte Carlo- Molecular Dynamics simulations are used to examine the interactions of various elemental species with GBs and any resultant segregation and elemental redistribution effects. Gibbsian excess quantities are used to quantify the results and reveal segregation behavior as a function of GB misorientation. Our approach provides avenues to account for defect-alloy interactions in MPEA design efforts.

J-36: GTA Weldability of Metastable Ferrous Medium-entropy Alloys with Various Welding Materials: Yoona Lee1; Sanghyeon Park1; Yoonsuk Choi1; Nokeun Park2; Youngsang Na3; Namhyun Kang1; 1Pusan National University; 2Yeungnam University; 3Korea Institute of Materials Science
     Due to the need to develop alternative energy resources, the need for developing materials with cryogenic properties used in the deep sea and polar regions increases. As conventional materials with these properties, austenitic stainless steel has used, but there are problems of hot cracking, stress corrosion cracking, and sensitization after welding. Therefore, high-entropy alloys (HEAs), which can overcome the limitations of conventional alloys, are in the spotlight. Also, ferrous medium-entropy alloys (MEAs) with more economical compared to HEAs and excellent cryogenic properties due to deformation-induced phase transformation by a metastable phase are being actively studied. To use such ferrous MEAs to the next-generation structural materials, it is necessary to develop welding materials, but there are no studies.In this study, welding materials suitable for metastable ferrous MEAs were developed. The mechanical properties and microstructural behavior of the welds with various welding materials at room and cryogenic temperature were examined.

J-37: High-density Nanoscale L12 Phase Strengthened FeNiCr-based Medium Entropy Alloys: Guanghui Yang1; Jinkyung Kim1; 1Hanyang University
    Coherent nanoprecipitation strengthened high entropy alloys (HEAs) exhibit considerably higher strength than the single-phase HEAs. However, the simultaneous achievement of ultrahigh strength and acceptable ductility is still challenging. The present work reports microstructures and mechanical properties of (Al, Ti)-added FeNiCr based medium entropy alloys. We focus on the evolution of microstructure and mechanical properties for each processing condition such as casting, hot rolling, homogenization, cold-rolling, and annealing. The high density of the nanoscale L12 phase was formed after cold-rolling and annealing. The density of the precipitates increases with increasing cold-rolling reduction probably due to nucleation of the precipitates at the defects formed upon cold-rolling. Further, partially recrystallized microstructures with fine grain size and a high density of precipitates could lead to superior strength-ductility balance of the material. We will discuss the microstructure-mechanical properties relationship of the investigated materials.

J-38: High-throughput Calculation of the Alloying Effects on the Thermodynamic Properties of Al2Cu10Fe20MnxNiyCrz High Entropy Alloys: Md Abdullah Al Hasan1; Xuesong Fan1; Seungha Shin1; Peter Liaw1; 1University of Tennessee
    High-entropy alloys (HEAs) offer huge compositional and microstructural spaces to explore for desirable physical properties while facing challenges due to high computational costs. Thermodynamic properties, specifically lower thermal expansion coefficients (CTEs) in HEAs are desirable, however, scarce in literature. In this research, we will implement high-throughput calculations by combining first-principles calculations and state-of-the-art machine learning techniques to examine the alloying effects on the HEAs to predict desirable thermodynamic properties. From both of our simulations and experiments, it was observed that increasing Cr or reducing Mn content in Al2Cu10Fe20MnxNiyCrz HEAs resulted in lowering CTEs at room temperature. Therefore, multiple alloying contents will be considered, and our approach will work as a closed-loop, integrating machine learning with these simulations and experiments to find lower CTEs over a wide temperature range of 300-1200 K. This work will enable fast and automated discovery of HEAs with optimal thermodynamic properties as well as high-temperature applications.

J-39: High-throughput CALPHAD-type Calculation in Design of Coherent Precipitate-strengthening Al-Co-Cr-Mo-Ti Refractory High Entropy Superalloys: Shao-Yu Yen1; Hideyuki Murakami2; Shih-kang Lin1; 1National Cheng-Kung University; 2National Institute for Materials Science
    Refractory high entropy superalloys (RSAs) are one of the most recent developments of structural materials for high temperature applications, which have microstructures with disordered BCC (A2) and ordered B2 phases. However, such kind of microstructures suffer from the poor stability at high temperature because they are formed from spinodal decomposition. Besides, exploration for RSAs in the multi-dimensional composition space with trial-and-error experiments is costly and time-consuming. The present work employs CALPHAD method combined with high-throughput calculation (HTC) to quickly search the desired compositions with A2+B2 phases. Considering oxidation resistance and thermal stability, Al-Co-Cr-Mo-Ti quinary system is selected as the prototype. Experiments were carried out for verification, and the results showed a good agreement with the calculations. We propose a new calculation approach for RSAs design and demonstrate that high-throughput CALPHAD-type calculation is a powerful and reliable method for next-generation material’s design.

J-40: High-throughput Creation of Refractory High-Entropy Alloys: Rayna Mehta1; Jesse Grant1; Tim Weihs1; 1Johns Hopkins University
    Refractory high entropy alloys are attractive for their mechanical properties at high temperatures. However, the vast compositional space presents a fabrication challenge: how does one quickly create hundreds of compositionally unique samples with bulk-like microstructures? Here we introduce a novel combinatorial method to do so by sputter depositing thick foils that can be processed and mechanically tested as free-standing samples at both low and high temperatures. The foils measure 10 to 200 microns in thickness, and they are annealed and rolled to produce bulk-like grain sizes and textures after removal from their substrates. In this study, we focus on Nb-Ti-Zr and Nb-Ti-Zr-Al alloys, and we screen the many samples based on their chemistry, phase, hardness, ductility, and oxidation. Through this methodology, we hope to find a range of compositions that yield single-phase, body centered cubic materials with strength, ductility, and oxidation resistance.

J-41: High Temperature B2 Precipitation of Ru-Containing Refractory Alloys: Haojun You1; Carolina Frey1; Sebastian Kube1; Kaitlyn Mullin1; Andrew Detor2; Scott Oppenheimer2; Tresa Pollock1; 1UCSB Pollock Group; 2GE Research
    Refractory Multi-Principal Element Alloys (RMPEAs) are a new class of structural alloys for extreme environments with the potential to push operating temperatures above 1200°C. However, alloys examined to date have been unable to achieve a balanced suite of properties at high temperature, primarily due to the lack of strengthening precipitates with high thermal stability. Recently, Ru-based B2 precipitates have been shown to be stable above 1200 °C. To further explore Ru as an alloying addition, the microstructures of a series of arc-melted equiatomic Ru-containing RMPEAs were analyzed via SEM and TEM. Microstructures of these materials in both their as-cast and annealed conditions have been characterized. XRD lattice parameters and hardness values (for both individual B2 phases via nano-indentation and the aggregate alloy) are also reported. Promising alloy compositions are identified.

J-42: In-Situ Investigation of Damage in the AlCoCrFeNi2.1 High Entropy Alloy: Cal Siemens1; David Wilkinson1; 1McMaster University
    The AlCoCrFeNi2.1 eutectic HEA (EHEA) is a duplex casting alloy, consisting of face-centered cubic (FCC) and body-centered cubic (BCC) phases, exhibiting high strength and moderate ductility. Various studies used alloying and thermomechanical processing approaches to improve this alloy’s mechanical properties. However, there has been little work published on the fundamental mechanisms controlling damage and fracture of this EHEA. This study uses in-situ techniques involving micro-digital image correlation (μ-DIC) and x-ray computed tomography (XCT) to characterize the distribution of deformation and damage evolution at the microscale while under strain. These methods were paired with scanning electron microscopy (SEM), nanoindentation, and fracture toughness to evaluate phase-specific composition, hardness, and defect sensitivity. We determine that micro-crack nucleation and propagation is a controlling fracture mechanism and have identified microstructural features that contribute to increased ductility of this EHEA following rolling of the as-cast structure. This suggests methods to improve ductility in future HEA development.

J-43: In-situ Quasi-static Deformation Studies of CoCrNi Multi-principal Element Alloys: Nathan Peterson1; John Copley2; Benjamin Ellyson1; Connor Rietema3; Francisco Coury; Francisco Coury4; Gustavo Bertoli4; Kester Clarke1; Amy Clarke1; 1Colorado School of Mines; 2Princeton University; 3Lawrence Livermore National Laboratory; 4Federal University of São Carlos
    Multi-principal element alloys (MPEAs), particularly those from the CoCrNi family, have been demonstrated to have both high strength and ductility at cryogenic and room temperatures. These alloys obtain their high toughness from plastic deformation mechanisms beyond slip, such as transformation and/or twinning induced plasticity (TRIP/TWIP). Due to the vast compositional landscape available for MPEAs, high throughput characterization methods are necessary to efficiently select new alloy compositions that exhibit TRIP and/or TWIP behavior. In-situ synchrotron x-ray diffraction measurements were performed at the Advanced Photon Source at Argonne National Laboratory to quantify the microstructural evolution in both equiatomic CoCrNi and a set of CoxCr40Ni60-x (x=30, 40, 50, 55 wt.%) MPEAs during quasi-static deformation at various temperatures between 23°C - 300°C to identify the active deformation mechanism(s) for different compositions and phase stabilities.

J-44: In-situ Tensile Testing Using Synchrotron Radiation in a CrCoNi Multi-principal Element Alloy: Gustavo Bertoli1; Benjamin Ellyson2; Amy Clarke2; Claudio Kiminami1; Francisco Coury1; 1Federal University of São Carlos; 2Colorado School of Mines
    Among multi-principal element alloys (MPEAs), CrCoNi system alloys have attracted significant attention. For the present study, the Cr40Co40Ni20 MPEA was selected due to the good combination of mechanical strength and ductility, in addition to a great grain refining strengthening component. Its single-phase face centered cubic (FCC) structure partially transforms to hexagonal close packed (HCP) phase by transformation-induced plasticity (TRIP) effect during straining, which provides enhanced ductility. For this study, this MPEA was produced, cold formed, and recrystallized under different conditions to obtain samples with different grain sizes. In-situ tensile testing using synchrotron radiation were carried out at the Advanced Photon Source (APS) at Argonne National Laboratory, IL, USA. The density of defects, crystallite size and phase fraction were evaluated throughout the deformation process. The influence of grain size on these parameters, as well as on the TRIP/TWIP activation, are discussed.

J-45: In Situ Neutron Diffraction Analyses of Dislocation Slip and Twinning Deformation in an Additively Manufactured CrCoNi Medium Entropy Alloy: Wanchuck Woo1; Hobyung Chae1; Soo Yeol Lee2; Stefanus Harjo3; Ke An4; 1Korea Atomic Energy Research Institute; 2Chungnam National University; 3Japan Atomic Energy Agency; 4Oak Ridge National Laboratory
    Recently in situ neutron diffraction experiments have been performed in an additively manufactured (AM) equiatomic CoCrNi medium-entropy alloy. Investigated the variations of the dislocation densities and twin fault probabilities under loading based on the faulting-embedded diffraction peak profile analyses. The results show that the initial dislocation density in AM (1.3 x 10^14 m-2) is suprisingly ~10 times higher than the conventional cast-wrought specimen (0.18 x 10^14 m-2). It increases significantly up to 17 x 10^14 m-2 in AM near fracture. On the other hand, the twin fault probability is much lower in AM (1.3%) than cast-wrought specimen (2.7%). It corresponds to the strengthening via dislocation and twinning of 600 and 180 MPa in AM, respectively. Such a dislocation slip dominant deformation mechanism in AM rather than twinning is relavant to the stacking fault energy (SFE). Details peak profile analyses and SFE results will be presented with EBSD and TEM observations.

Investigation on Formation of Duplex Microstructure and Mechanical Properties in CrMnFeCoNiAlxTiy High-entropy Alloy: Jongtae Kim1; Juree Jung1; Jinwoo Seok1; Junwoo Song1; Jeongeun Kim2; Gian Song2; Junhee Han1; 1KITECH; 2Kongju National University
    CrMnFeCoNi High-entropy-alloys (HEAs) has a single phase of Face-Centered-Cubic (FCC) structure, which shows high ductility, but low strength. Recently, several studies have reported that the Al addition to CrMnFeCoNi HEA induces a phase transition from FCC to Body-Centered-Cubic (BCC) structure due to their large atomic radius difference. The formation or increase of the BCC phase increases strength, but significant reduction in ductility follows. In this study, we developed a duplex-structured HEA by adding alloying elements and heat treatment with an objective to improve the strength and plasticity simultaneously. For the formation of duplex-structured alloy, proper amount of Al and Ti elements were added to CrMnFeCoNi HEA and then thermo-mechanical process was performed based on thermodynamic calculation and differential scanning calorimetry (DSC) results. Microstructure and mechanical properties were investigated by X-ray diffraction, scanning electron microscopy, electron backscatter diffraction, transmission electron microscopy, and universal testing machine.

J-46: Irradiation-induced Segregation in Complex Concentrated Alloys: Daniele Fatto Offidani1; Anshul Kamboj1; Emmanuelle Marquis1; 1University of Michigan - Ann Arbor
    Multi-principal element alloys (MPEAs) have been proposed as candidate materials for nuclear applications due to their superior mechanical properties and corrosion resistance. Yet, the literature concerning the microstructural and chemical changes in these alloys upon irradiation remains limited. Therefore we focus here on the effects of irradiation near and at grain boundaries in MPEAs, with an emphasis on radiation-induced segregation. To this end, a series of CrFeNi/based MPEAs was irradiated using heavy ions. The analysis and comparison of the chemical composition of the grain boundaries in the irradiated and non-irradiated alloys provide insights into the behaviors of point defects in different alloy chemistries.