High Entropy Alloys VIII: Structures and Mechanical Properties
Sponsored by: TMS Functional Materials Division, TMS Structural Materials Division, TMS: Alloy Phases Committee, TMS: Mechanical Behavior of Materials Committee
Program Organizers: Peter Liaw, University of Tennessee; Michael Gao, National Energy Technology Laboratory; E-Wen Huang, National Chiao Tung University; Srivatsan Tirumalai; Xie Xie, FCA US LLC; Gongyao Wang, Globus Medical
Wednesday 2:00 PM
February 26, 2020
Room: Mission Hills
Location: Marriott Marquis Hotel
Session Chair: David Shifler, Office of Naval Research; Marc Meyers, University of California, San Diego
2:00 PM Cancelled
Microstructure and Mechanical Property of FCC HEA with L12 -strengthened Between Cryogenic and Elevated Temperatures: Che-Wei Tsai1; Chia-Ming Kuo1; 1National Tsing Hua University
The HEA with FCC matrix phase and L12 precipitates phase were studied. It is found the strain-induced cellular structures were observed in this alloy after thermomechanical treatment, and cellular structures can be eliminated by a slow cooling process. After that, the structures of spherical L12 precipitates uniformly distributed in the matrix were obtained. The present HEAs without cellular structures showed more superior mechanical properties at temperatures from 293K to 1073 K than those with cellular structures. The tensile results show a good combination of strength and ductility at 873K. Furthermore, cryogenic temperatures tensile properties and the corresponding fracture analyses were conducted and investigated. There are multiple-layered stacking faults after 77K tensile test, which act as work-hardening source, can give rise to the yield strength and ultimate tensile strength. The mechanical twinning is also observed in the matrix, which attributes to the ductility of 33% increment at cryogenic temperature.
2:20 PM
Concurrent TWIP-TRIP, Short-range Order and Strain Localization in Single-crystal NiCrCo Medium Entropy Alloy Drives Exceptional Mechanical Behavior: Sezer Picak1; Prashant Singh2; Aayush Sharma2; Yuri I. Chumlyakov3; Duane D. Johnson2; Raymundo Arroyave1; Ibrahim Karaman1; 1Texas A&M University; 2Lowa State University; 3Siberian Physical Technical Institute
High entropy alloys are new class of multi-component systems that form solid-solution phases with unique mechanical behavior. We report that exceptional mechanical properties of a face-centered-cubic NiCoCr medium entropy alloy are driven by interplay of deformation twinning, stress/strain-induced martensitic transformation, short-range ordering and strain-localization. Our molecular dynamics simulations suggest simultaneous twinning and martensitic transformation under uniaxial tensile deformation. We also predict favorable short-range order wave-vector [W = (1 ½ 0)] (usually) responsible for planar slip and anomalous work hardening in f.c.c. based alloys using first-principles thermodynamic linear-response. Ex-situ transmission electron microscopy and diffraction experiments confirm our predictions and establish that the simultaneous activation of twinning, martensitic transformation, short-range ordering and deformation-induced strain localization in NiCoCr alloys maintain high-strength, ductility and toughness. These concurrent strengthening mechanisms provide strategies to further improve such properties in this new class of alloys.
2:40 PM Invited
Non-equiatomic, Multi-phase TRIP/TWIP Multi-principal Element Alloys: Amy Clarke1; Francisco Coury2; John Copley1; Yaofeng Guo1; Jonah Klemm-Toole1; Benjamin Ellyson1; Jinling Gao3; Chandler Becker1; Brian Milligan1; Christopher Finfrock1; Chloe Johnson1; Kester Clarke1; Wayne Chen3; Niranjan Parab4; Tao Sun4; Kamel Fezzaa4; Michael Kaufman1; 1Colorado School of Mines; 2Universidade Federal de São Carlos; 3Purdue University; 4Advanced Photon Source, Argonne National Laboratory
Multi-principal element alloys (MPEAs), without a primary alloying addition like conventional alloys, are stimulating the exploration of novel alloying, microstructure, and property designs. Although MPEAs with remarkable properties have been reported, the focus to date has primarily been on the quest for single-phase, equiatomic alloys that exhibit solid solution strengthening. Yet, opportunity exists to find non-equiatomic alloys with maximized solid solution strengthening and non-equiatomic alloys with multi-phase microstructures that exhibit additional strengthening mechanisms. Here we focus on high-throughput, thermodynamic modeling to predict non-equiatomic Co-Cr-Ni alloys that exhibit TRansformation Induced Plasticity (TRIP) and/or TWinning Induced Plasticity (TWIP) to improve toughness for blast resistance. We seek to fundamentally understand TRIP/TWIP deformation mechanisms as a function of strain rate by in-situ synchrotron x-ray imaging and/or diffraction during quasi-static and/or dynamic compression and tensile testing, along with complementary ex-situ microstructural and mechanical characterization, to ultimately design microstructural and mechanical response.
3:00 PM
Microstructural Characterizations and Mechanical Properties of CrFeNiMn and NbTaTiV High Entropy Alloys: Mohamed Elbakhshwan1; Michael Moorehead1; Calvin Parkin1; Bo-Shiuan Li2; David Armstrong2; Angus Wilkinson2; Xuan Zhang3; Chuan Zhang4; Kumar Sridharan1; Adrien Couet5; 1University of Wisconsin Madison; 2University of Oxford; 3Argonne National Laboratory; 4CompuTherm LLC.; 5University of Wisconsin- Madison
High entropy alloys (HEAs) are composed of multi-principal elements in equal or near-equal atomic ratios in typically single-phase solid solution. Some HEAs have shown desirable properties for nuclear applications such as suppression to radiation induced segregation, low defect cluster sizes, and high swelling resistance. However, the properties of the HEAs have to be fully understood before their implementation in nuclear reactors. This study focuses on the microstructural characterizations, mechanical properties, and high temperature stability of single phase Cr18Mn27Fe27.5Ni27.5, Cr15Mn15Fe35Ni35, and NbTiVTa HEAs. High temperature mechanical properties were evaluated using tensile and four-point bending testing. The FCC Cr18Mn27Fe27.5Ni27.5 alloy experienced phase separation at 700ºC, while the Cr15Mn15Fe35Ni35 alloy remained stable. The BCC NbTaTiV HEA shows some ductility at room temperature which increased with heating up to 400ºC. Experimental analysis of phase evolution results have been combined with CALPHAD modeling to guide the search for new and improved HEAs for nuclear applications.
3:20 PM Invited
Development of CuFeMnNi-based High Entropy Alloys Using CALPHAD Approach and Thermomechanical Processing: Xuejun Huang1; Jiashi Miao1; Alan Luo1; 1Ohio State University
CuFeMnNi-based high entropy alloys were designed and optimized using CALculation of PHAse Diagrams (CALPHAD) approach. These high entropy alloys in as-cast condition exhibit good tensile properties. The homogenization process was selected based on calculated phase diagrams. Improvement on strength and ductility was achieved by cold rolling in combination of annealing at different temperature. Aluminum was added to enhance the mechanical properties of the base alloy through precipitation strengthening. The corrosion resistance of CuFeMnNi-based high entropy alloys can be improved by the addition of chromium. The strengthening mechanism in CuFeMnNi-based high entropy alloys was revealed using advanced electron microscopy techniques.
3:40 PM Break
4:00 PM Invited
On the Damage Tolerance of TRIP, TWIP and Dual-phase High-entropy Alloys: Bernd Gludovatz1; Hyun Seok Oh2; Eun Soo Park2; Robert Ritchie3; 1UNSW Sydney; 2Seoul National University; 3Lawrence Berkeley National Laboratory
Compositionally complex alloys, often termed high-entropy alloys, are an intriguing new class of materials that can crystallize as single-phase solid solutions with simple crystal structures despite containing high concentrations of elements with very different crystal structures. Additionally, they can display a good combination of mechanical properties making them attractive for a wide range of applications. Based on our work on the CrMnFeCoNi alloy which exhibits an excellent combination of strength, ductility and fracture toughness at ambient to cryogenic temperatures, consistent with its deformation modes of planar dislocation slip and deformation-induced nano-twinning, we will examine compositionally modified variations of this material. We will show how their failure resistance develops in the same temperature range when compositionally triggered deformation mechanisms such as transformation induced plasticity (TRIP) or twinning induced plasticity (TWIP) are enabled and additionally compare their behavior to a similar alloy that contains a second phase.
4:20 PM Invited
Dynamic Behavior of CrMnFeCoNi High-entropy Alloy: Marc Meyers1; Zezhou Li1; Shiteng Zhao2; Carlos Ruestes3; Bingfeng Wang4; Yong Liu4; Peter Liaw5; Wen Yang1; Robert Ritchie2; 1University of California San Diego; 2Lawrence Berkeley Laboratory; 3CONICET & Universidad Nacional de Cuyo; 4Central South University; 5The University of Tennessee
High impact resistance of CrMnFeCoNi high-entropy alloy (HEA) is expected due to its excellent behavior under high-strain-rate compression. Its underlying deformation mechanisms under dynamic loading have been identified by both experiments and simulations. The high strain-hardening ability of the CrMnFeCoNi HEA, enabled by solid-solution hardening, forest dislocation hardening and twinning hardening, a marked strain-rate sensitivity and modest thermal softening, result in an excellent resistance to shear localization. For the CrMnFeCoNi alloy, a shear strain of ~7 has been discovered as required for the shear-band propagation (using a hat-shaped specimen that enables one single shear band to initiate and grow). Simultaneously, nanotwinning plays a dominant role on deformation during shock hardening (front surface) and spalling (rear surface) of the CrMnFeCoNi alloy employed on laser ablation shock compression. The remarkable high-strain-rate behavior of CrMnFeCoNi HEA and its deformation mechanisms make it a significant candidate for ballistic applications.
4:40 PM
Unique Elastic and Plastic Deformation Behavior of a Ductile Refractory High-entropy Alloy at Room and Elevated Temperatures: Chanho Lee1; Gian Song2; Yi Chou3; George Kim4; Wei Chen4; Ke An5; Yi-Chia Chou3; Peter K. Liaw1; 1University of Tennessee; 2Kongju National University; 3National Chiao Tung University; 4Illinois Institute of Technology; 5Oak Ridge National Laboratory
In order to concretely verify the deformation behaviors of BCC refractory HEAs, numerous efforts have been made, such as the investigation on elastically-isotropic deformation and excellent room-temperature ductility, using computational simulations. However, these predictions of elastic and plastic deformation behavior are still under discussion, due to the lack of experimental verifications. In this study, we have investigated the elastic-deformation behavior of a single BCC NbTaTiV refractory HEA at elevated temperatures, using integrated in-situ neutron-diffraction experiments, density functional theory (DFT) calculations. The single-crystal elastic moduli were determined from the diffraction elastic moduli, using the Kroner model. The type of mobile dislocation as a function of macrostrains are quantitatively calculated and predicted by Williamson-hall plot profile modeling. It is found that the edge dislocations can be the dominant mobile dislocation type for the BCC refractory HEAs during plastic deformation. The type of dominant mobile dislocation was further examined by transmission-electron-microscopy (TEM).
5:00 PM Invited
Studies on Microstructure, Hardness and Corrosion Behavior of the Cu-Fe-Ti-Zr-Nix High Entropy Alloys: Po-Cheng Kuo1; William Yu1; Hsien-Ming Hsiao2; Satoshi Iikubo3; Yee-Wen Yen4; 1Department of Materials Science and Engineering, National Taiwan University of Science and Technology; 2Institute of Nuclear Energy Research; 3Graduate School of Life Science and Systems Engineering, Kyushu Institute of Technology; 4National Taiwan University of Science and Technology
Cu-Fe-Ti-Zr high entropy alloys (HEAs) systems could give enormous attention with extreme mechanical and corrosion resistance porperties. In this research, Cu-Fe-Ti-Zr-Nix alloys were prepared by arc melting and annealing at 900°C to investigate the effect of Ni content on microstructure, hardness, and corrosion resistance behavior. As the Ni content is increased, the microstructure was changed from B2_BCC and Laves_C14 to FCC and B2_BCC at Ni0.1 and Ni0.3, Laves_C14 at Ni0.5, and FCC, B2_BCC, Cu51Zr14, and Laves_C14 at Ni0.8 and Ni1.0. The intermetallic compounds (IMCs) which were caused by the refractory elements (Ti and Zr) and atomic size difference were found in dendritic microstructure in the Cu-Fe-Ti-Zr-Nix alloys. The hardness and corrosion behavior of the Cu-Fe-Ti-Zr-Nix alloys were revealed that when Ni content was increased, the hardness of the Cu-Fe-Ti-Zr-Nix alloys was gradually decreased, and better corrosion resistance in NaCl solution was observed.
5:20 PM Invited
Integrating Theory and Experiment in the Design of Multiprincipal Element Alloys: Mu Li1; Zhaohan Zhang1; Arashdeep Thind1; Rohan Mishra1; Katharine Flores1; 1Washington University in St. Louis
Multiprincipal element alloys (MPEAs) have garnered significant interest as potential next-generation structural materials due to their unique lack of a dominant solvent species and the resulting potential for deviations from conventional structure-property models. In this work, we apply high-throughput alloy synthesis and screening methods to rapidly identify potential MPEA compositions of interest, and use density functional theory (DFT) calculations to gain a better understanding of the origin and stability of the observed structures. In one model refractory system, NbTixVZr, we observe that the microstructure of the ternary alloy (x = 0) consists of a BCC solid solution and hexagonal (C14) and cubic (C15) Laves phases. The addition of Ti destabilizes the Laves phases, resulting in a single BCC solid solution in the quaternary alloy. Micromechanical and STEM measurements are used to examine deformation mechanisms, particularly the role of stacking faults observed in the Laves phases. Implications for the selection of additional alloying elements will be discussed.