High Entropy Materials: Concentrated Solid Solutions, Intermetallics, Ceramics, Functional Materials and Beyond III: Processing and Properties II
Sponsored by: TMS: Nanomaterials Committee
Program Organizers: Yu Zhong, Worcester Polytechnic Institute; 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; Mitra Taheri, Johns Hopkins University; Amy Clarke, Los Alamos National Laboratory
Wednesday 8:00 AM
October 12, 2022
Room: 324
Location: David L. Lawrence Convention Center
Session Chair: Hyoung Seop Kim, POSTECH; Peter Liaw, University of Tennessee
8:00 AM Keynote
Exploring Properties and Relationships in High Entropy Alloys: David Shifler1; 1Office of Naval Research
High entropy alloys (HEAs) are alloys with five or more principal elements that have a concentration between 5 and 35 at.% with other minor (< 5At%) elements. HEAs have random liquid or random solid solution states that have significantly higher mixing entropies than those in conventional alloys. Because there are multiple principal element comprising these alloys, HEAs can possess special properties which may include high strength/hardness, outstanding wear resistance, exceptional high-temperature strength, good structural stability, and/or good corrosion and oxidation resistance.HEAs cover a huge compositional space, thus, comprehensive, multidisciplinary, high throughput computational, experimental and characterization approaches are needed. The goal is to create multi-variable physics- and chemical-based models and tools to establish the fundamental science base for these alloys. Our existing understanding of physical metallurgy, mechanics, passivity, phase stability, and heat treatments will face a challenge in our pursuit of interpreting the structure-processing-property relationships of such multi-element alloys.
8:30 AM Invited
Grain Refinement and Nano-scale Precipitates in Non-equiatomic CoCrFeNiMo Medium-entropy Alloy: Hyoung Seop Kim1; Hyeonseok Kwon1; 1Pohang University of Science and Technology
A strategy to improve the tensile properties of Co17.5Cr12.5Fe55Ni10Mo5 (at%) medium-entropy alloy through high-pressure torsion and subsequent annealing is presented in this work. Microstructural study revealed that the high-pressure torsion process led to the formation of fine grains (< 1 μm) and profuse nano-scale Mo-rich μ-phase precipitates. And resultantly, the yield strength of the alloy was tuned from ~400 MPa to ~1 GPa, while preserving reasonable uniform elongation over 15%. The combination of strengthening from grain refinement and precipitation contributed to the excellent strength, while the post-HPT annealing provided substantial ductility.
9:00 AM
Laser Welding of CoCrFeMnNi High Entropy Alloy to Inconel 718: Joao Oliveira1; 1FCT-UNL
Dissimilar laser welding of the CoCrFeMnNi to Inconel 718 was successfully performed. Microstructure characterization by means of electron microscopy and high energy synchrotron X-ray diffraction were used to evaluate joint. Moreover, thermodynamic simulatuion were employed to further rationalized the microstructure evolution within the welded region. Digital image correlation was used to determine how the different regions of the joints (base material, heat affected zones and fusion zone) deformed during tensile testing. High strength and ductility were obtained in the laser welded joints upon optimization of the process parameters. A correlation between process parameters, microstructure evolution and mechanical properties was established. The sound joints obtained in this work may open new potential applications for high entropy alloys in high demanding structural applications.
9:20 AM
Mechanical and Oxidation Behavior of Hf-25Ta-5X Refractory Complex Concentrated Alloys: Eric Payton1; Tinuade Daboiku1; Satish Rao1; Oleg Senkov1; 1Air Force Research Laboratory
Recent work by Perepezko and Yang has indicated that Hf-27Ta forms an adherent and thermal-shock resistant oxide (Hf6Ta2O17) during high temperature oxidation, and Senkov et al have shown that additions of Mo and W while holding this Hf:Ta ratio can increase the high temperature strength in this alloy system. The protective oxide is predicted using ab-initio calculations to also be formed preferentially at lower temperatures, <1500 degrees C. In the present work, we investigate the mechanical properties and oxidation behavior of arc-melted and hot isostatically pressed Hf-25Ta-5X alloys where X=Nb, Zr, Cr, W, Mo, or Mo+W at temperatures lower than 1500 degrees C. The observations are compared against other refractory complex concentrated alloys. It is observed that oxidation behavior of all Hf-25Ta-5X alloys investigated are inferior to Nb-18Ti-10W, and formation of a protective layer of Hf6Ta2O17 is not observed. The underlying reasons for this observation are explored and discussed.
9:40 AM
Microstructural Characterization and Oxidation Resistance in Multi FCC Principal Element Alloys: Mckenna Hitter1; Shailendra Varma1; 1University of Texas at El Paso
Multi FCC principal element alloys have been created using equiatomic Al-Cu-Ni-Mn (RB=12) and Al-Cu-Ni-Mn-Si (RB=74)systems. Microstructural characterization in both as received and oxidized conditions has been carried out. We have the evidence of four microconstituents present that are rich in : (a) Mn , (b) Ni and (c) Al-Cu-Ni in quaternary and Al-Cu-Mn in quinary alloys, and (d) eutectic. Incorporation of Si results in the formation of an additional microconstituent in the form eutectic. The alloys were subjected to oxidation in air at 600, 700, and 800oC for 24 hours. Excellent oxidation resistance up to 800oC has been observed for this alloy. The oxide scales and changes in the microstructures evolved during oxidation have been delineated using back-scattered electron mode in an SEM, EDS, XRD, and color x-ray mapping.
10:00 AM Break
10:20 AM
Phase Evolution and Oxidation Study of Combinatorially Designed Hf-Al-Si Refractory Complex Concentrated Alloy for High Temperature Applications: Sophia Cooper1; Samir Aouadi1; Andrey Voevodin1; Anindya Ghoshal2; Victoria Blair2; Marcus Young1; 1University of North Texas; 2US Army Research Laboratory
Refractory complex concentrated alloys (RCCAs) are a unique group of materials defined by shared principality between all alloying elements and the resulting remarkable mechanical properties in high temperature (>1000°C) applications. RCCA systems can be selected using high-throughput processing which allows for simultaneous characterization and testing over a range of compositions. Compositionally graded Hf-Al-Si coatings produced on a Si wafer were compositionally mapped using ESEM with EDS to identify the relative compositions as a function of position on the wafer. The RCCA wafers were subsequently heat treated at various temperatures to investigate any phase changes and oxidation behavior at elevated temperatures. Characterization of the RCCA was performed after heating using ESEM with EDS, XRD, and XPS to identify the microstructure, elemental distribution, phases, and oxidative states present across the alloy as a function of compositional gradient and to determine an alloy composition range with the least amount of high temperature oxidation.
10:40 AM
3D Ink-extrusion Printing of CoCr(Cu)FeNi High-entropy: Dingchang Zhang1; Christoph Kenel1; David Dunand1; 1Northwestern University
3D ink extrusion printing is an additive manufacturing (AM) method where a powder-loaded liquid ink is extruded layer by layer to form complex shaped 3D objects; the green material is then isothermally sintered into a densified part. Here, we fabricate micro-lattices of two high-entropy alloys (equiatomic CoCrFeNi and CoCrCuFeNi) by extrusion printing of ink containing a blend of binary oxides, followed by reduction in hydrogen and sintering. This method avoids the problems of residual stress (inducing cracks) and textured microstructure that occur in laser/electron-based AM methods; it also offers the use of submicron metal oxide powders which achieve very high surface quality after sintering. We focus on (i) measuring the kinetics of co-reduction of oxides and alloy interdiffusion by in-situ X-ray diffraction, (ii) understanding the microstructural evolution after solid and liquid sintering, and (iii) studying the compressive properties of micro-lattices, via experimental measurements and numerical finite element modeling.
11:00 AM
Experimental Determination of Mid-temperature Phases in Refractory Multi-Principal Element Ternary Alloys for Thermodynamic and Solid Solution Strengthening Modeling: Adira Balzac1; Benjamin Ellyson1; Kester Clarke1; Amy Clarke1; 1Colorado School of Mines
Novel multi-principal element alloys in the NbTaTi and NbTiZr families are promising candidates for developing high-strength refractory alloys. For these refractory ternaries, there are gaps in the experimental data in literature at mid-temperature ranges between about 900 and 1700 °C, which limits the modeling that can be done to predict phase equilibria to specific compositions, usually equimolar, that have been studied. We propose to study the equilibrium phases present in NbTaTi and NbTiZr at off-equimolar compositions through homogenization and annealing heat treatments at these temperatures to produce phase equilibria data that can be used to develop databases further for thermodynamic and solid solution strengthening modeling. We will also investigate the microstructures that develop because of thermomechanical processing and develop pathways to control these microstructures.
11:20 AM
High-temperature Oxidation and Mechanical Behavior of Ta-Ti-Cr Concentrated Refractory Alloys: Noah Welch1; Maria Quintana1; Todd Butler2; Peter Collins1; 1Iowa State University; 2Air Force Research Laboratory, WPAFB
There is an ever-growing need for high temperature materials that can outperform Ni-base superalloys in extreme environments (>1000°C-1150°C). While dilute refractory alloys generally exhibit suitable mechanical strength at much higher temperatures, their oxidation resistance is severely lacking. However, concentrated refractory alloys have a tendency to form favorable complex oxides that improve oxidation resistance. The oxidation behavior of four Ta-Ti-Cr alloys (TaTiCr, Ta4Ti3Cr, Ta2TiCr, and Ta4TiCr3) have been investigated to elucidate the role of constituent concentration on microstructures and resulting oxidation performance and mechanical behavior. These four alloys have been tested for 24 hours at 1200°C and show drastically different oxidation behaviors, with the TaTiCr alloy exhibiting superior oxidation resistance. These alloys were also mechanically tested (compression) in the 20-1200°C range to understand the high-temperature performance in atmospheres containing oxygen.