High Entropy Materials: Concentrated Solid Solutions, Intermetallics, Ceramics, Functional Materials and Beyond II: Processing and Properties I
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
Tuesday 2:00 PM
October 19, 2021
Room: B131
Location: Greater Columbus Convention Center
Session Chair: Michael Mills, Ohio State University
2:00 PM Invited
Insights into the Deformation Processes of a Refractory Complex Concentrated Alloy Exhibiting B2-type Order: Jean-Philippe Couzinie1; Milan Heczko2; Veronika Mazanova2; Oleg Senkov3; Rajarshi Banerjee4; Maryam Ghazisaeidi5; Michael Mills2; 1Université Paris Est & Center for Electron Microscopy and Analysis, The Ohio State University; 2Center for Electron Microscopy and Analysis, The Ohio State University; 3Materials and Manufacturing Directorate, Air Force Research Laboratory, Wright-Patterson AFB; 4University of North Texas; 5The Ohio State University
Refractory complex concentrated alloys (RCCAs) are currently among the most studied materials in the high-entropy field as they retain high mechanical properties up to 1000°C. The ordered B2 phase plays a key role in some of RCCAs behavior, and promising compositions are found in systems for which it is present, whether the B2 phase is continuous or forms coherent precipitates in the matrix. As they are currently seen as interesting candidates for future structural applications, some basic challenges have to be addressed. The understanding of the deformation mechanisms and of the influence of order on those mechanisms is one of them. In that respect, the present talk aims at giving some insights into the deformation processes of the Al0.5NbTa0.8Ti1.5V0.2Zr material after compressive testing at room temperature and 600°C. Detailed analysis of the defects governing the plastic deformation will be reported and discussed in light of the transmission electron microscopy observations.
2:20 PM Invited
Deformation Behavior in the Refractory High-entropy Alloys: Chanho Lee1; George Kim2; Yi Chou3; Michael Gao4; Ke An5; Gian Song6; Yi-Chia Chou3; Wei Chen2; Saryu Fensin1; Peter Liaw7; 1Los Alamos National Laboratory; 2Illinois Institute of Technology; 3National Chiao Tung University; 4National Energy Technology Laboratory/Leidos Research Support Team; 5Oak Ridge National Laboratory; 6Kongju National University; 7University of Tennessee
Single-phase solid-solution refractory high-entropy-alloys (HEAs) show remarkable mechanical properties, such as high yield strength with significant softening resistance at elevated temperatures. Hence, the in-depth study of the deformation behavior for body-centered-cubic (BCC) refractory HEAs is a critical issue to explore the uncovered/unique deformation mechanisms. We have investigated the elastic- and plastic-deformation behaviors of a single BCC NbTaTiV refractory HEA at elevated temperatures, using integrated experimental efforts and theoretical calculations. The in-situ neutron-diffraction results reveal a transition of the elastic-deformation feature from isotropic to anisotropic modes at elevated temperatures. The single-crystal elastic-moduli and macroscopic Young’s, shear and bulk moduli were determined from the in-situ neutron diffraction, showing the great agreement with first-principles calculations, machine-learning, and resonant-ultrasound spectroscopy results. Furthermore, the edge-dislocation-dominant plastic-deformation behaviors, which are different from conventional BCC alloys, have been quantitatively described by the Williamson-Hall plot profile modeling, which is further experimentally verified by the high-angle-annular-dark-field (HAADF) scanning-transmission-electron-microscopy (STEM).
2:40 PM
A Low-temperature Chemical/Powder Metallurgical Route for Generating Fine-grained Refractory Complex Concentrated Alloys: Kenneth Sandhage1; Sona Avetian1; Mario Caccia1; Michael Titus1; 1Purdue University
While Ni-based superalloys exhibit attractive combinations of mechanical and chemical properties for use in high-temperature corrosive environments, such as in jet engines and in turbines for power generation, the desire to further enhance turbine performance by raising turbine inlet temperatures beyond the capabilities of such Ni-based superalloys has led to interest in refractory complex concentrated alloys (RCCAs) as next-generation metallic materials with a potential for withstanding such extreme environments. In our work, a low-temperature, chemical/powder metallurgical (CPM) synthetic route has been developed to generate fine-grained ternary and higher order RCCAs, with the aim of improving the high-temperature mechanical behavior and oxidation resistance of such RCCAs. As a proof of concept, this CPM process has been used to generate fine-grained W-Mo-Cr-based alloys. The influences of CPM processing conditions on the microstructure and microchemistry of such alloys, and on the resulting mechanical and oxidation behavior, will be discussed.
3:00 PM
The Cyclic Plastic Strain Localization and the Fatigue Crack Initiation in Equiatomic CrCoNi Medium-entropy Alloy: Veronika Mazanova1; Milan Heczko1; Connor Slone2; Shih Mulaine1; Easo P. George3; Maryam Ghazisaeidi1; Jaroslav Polak4; Michael J. Mills1; 1The Ohio State University; 2Exponent; 3Oak Ridge National Laboratory; 4Institute of Physics of Materials CAS
Multi-principal-element alloys became a topic of significant interest thanks to their outstanding mechanical properties at room and low temperatures. However, there is still a lack of information about their fatigue properties. In current work, the attention is focused on model system, equiatomic CrCoNi alloy in fully recrystallized microstructural state which combines good cyclic strength with superior resistance to cyclic plastic deformation. The cyclic plastic localization and its role in the fatigue crack initiation during low cycle fatigue loading were studied. A sophisticated experimental workflow was designed to extract information from the surface and the bulk of tested material using a combination of SEM, EBSD, ECCI, FIB, and HR-STEM. High fraction of annealing twin and the fatigue-induced deformation twin boundaries were preferential sites for localized cyclic plastic strain. Moreover, stress concentrations near deformation twins led to activation of TWIP and TRIP plasticity and early, well-development of surface relief.
3:20 PM
The Cyclic Plastic Response and the Fatigue Induced Microstructural Changes of Equiatomic CrCoNi Medium-entropy Alloy: Milan Heczko1; Veronika Mazánová1; Connor Slone2; Ivo Kuběna3; Mulaine Shih1; Tomáš Kruml3; Easo George4; Maryam Ghazisaeidi1; Jaroslav Polák3; Michael Mills1; 1The Ohio State University; 2Exponent; 3Institute of Physics of Materials CAS; 4Oak Ridge National Laboratory
Equiatomic CrCoNi alloy was subjected to strain-controlled low cycle fatigue tests at room temperature in a wide interval of strain amplitudes. Fatigue hardening/softening curves, cyclic stress-strain curves and fatigue life curves were evaluated. The evolution of the internal critical stresses and the effective saturated stress during cyclic loading was analyzed using a generalized statistical theory of the hysteresis loop. The deformation substructure was studied by atomic resolution electron microscopy and correlated with the cyclic response. Correlation of mechanical test data, modeling and characterization reveals details of the deformation mechanisms such as highly planar slip, deformation twinning and FCC-HCP transformation, which govern cyclic strength, cyclic plastic response and the fatigue life. Performance of the CrCoNi alloy, which is characterized by good cyclic strength combined with superior resistance to cyclic plastic deformation, is compared and discussed in relation to other structural alloys used in real service conditions.
3:40 PM Invited
Discontinuous Precipitation Leading to Nano-rod Intermetallic Precipitates in High Entropy Alloys Results in an Excellent Strength-ductility Combination: Sriswaroop Dasari1; Abhishek Sharma1; Bharat Gwalani1; Yao-Jen Chang2; Abhinav Jagetia1; Vishal Soni1; Stephane Gorsse3; An-Chou Yeh2; Rajarshi Banerjee1; 1University Of North Texas; 2National Tsing Hua University; 3University of Bordeaux
The phenomenon of discontinuous precipitation (DP) leading to the formation of nano-rod FCC (γ) + L12 (γ’) colonies, has been typically considered deleterious for mechanical properties. However, the present study shows clear evidence that substantially large fractions of FCC + nano-rod L12 microstructure within thermo-mechanically processed high entropy alloys (HEA) or complex concentrated alloys (CCA) of compositions, Al0.2Ti0.3Co1.5CrFeNi1.5 and Al0.3Ti0.2Co0.7CrFeNi1.7, formed via recrystallization coupled with discontinuous precipitation, can lead to excellent room temperature strength and ductility combinations. Further, the extent of thermomechanical processing can be engineered to modify the phase transformation pathway from homogenous L12 precipitation to discontinuous L12 precipitation in the same HEA. The predominantly FCC + nano-rod L12 microstructures in these alloys exhibit yield stresses upto ~1.6 GPa, with good tensile ductility of ~15%, making them some of the best combinations of room temperature tensile properties for FCC-based HEAs, that have been reported to date.
4:00 PM
Deformation Mechanisms in the Medium Entropy Alloy CoCrNi: Effects of Lattice Distortion and Chemical Short-range Order: Wu-Rong Jian1; Shuozhi Xu1; Yanqing Su2; Irene Beyerlein1; 1University of California, Santa Barbara; 2Utah State University
The medium entropy alloy (MEA) CoCrNi has been shown to exhibit an exceptional combination of tensile strength, ductility, and toughness. By using a combination of molecular dynamics, kinetic Monte Carlo, and crystal defect analysis, we investigate the effects of lattice distortion (LD) and chemical short-range order (CSRO) on the nucleation and evolution of dislocations and twins in single crystalline and nanocrystalline CoCrNi under uniaxial tension. For comparison, we repeat calculations on a hypothetical pure A-atom alloy with the same bulk properties of the nominal MEA but no LD or CSRO. We find that LD and CSRO have different effects on nucleation and propagation of Shockley partial dislocations. For instance, LD tends to lower the strain for dislocation nucleation, while higher degrees of CSRO tend to increase it. After yield, twin nucleation is promoted in MEAs, due to the reduced mobility resulting from LD and CSRO.