Innovations in High Entropy Alloys and Bulk Metallic Glasses: An SMD & FMD Symposium in Honor of Peter K. Liaw: High Entropy Alloys: Alloy Design and Processing
Sponsored by: TMS Functional Materials Division, TMS Structural Materials Division, TMS: Alloy Phases Committee
Program Organizers: Michael Gao, National Energy Technology Laboratory; E-Wen Huang, National Chiao Tung University; Yanfei Gao, University of Tennessee-Knoxville; Robert Maass, Federal Institute of Materials Research and Testing (BAM); Hahn Choo, University of Tennessee; Yunfeng Shi, Rensselaer Polytechnic Institute; Soo Yeol Lee, Chungnam National University; Xie Xie, FCA US LLC; Gongyao Wang, Globus Medical; Liang Jiang, Yantai University
Monday 2:30 PM
February 24, 2020
Room: Marina Ballroom G
Location: Marriott Marquis Hotel
Session Chair: Liang Jiang, Yantai University ; Soo Yeol Lee, Chungnam National University
2:30 PM Invited
Alloying Effects on Mechanical Properties of CoCrFeNi-based γ'-Strengthened Multi-principal Element Alloys for Elevated Temperature Applications: Akane Suzuki1; Shenyan Huang1; Doug Konitzer2; 1GE Research; 2GE Aviation
Microstructure, phase stability, tensile properties, creep and oxidation resistance of CoCrFeNi-based multi-principal element alloys were explored to understand alloying effects and to assess advantages against Ni-based superalloys. Alloys containing combinations of γ'-Ni3(Al,Ti) formers (Al and/or Ti) and a refractory element (Nb, Mo or Ta) to form additional strengthening precipitates were prepared and hot rolled to a sheet form, followed by solution and precipitation hardening treatments. Tensile and creep tests at 760 and 871°C showed presence of the γ' precipitates is the primary contributor. Laves and σ phase precipitates in alloys containing Nb and Mo, respectively, are useful in suppressing formation and coalescence of cavities along grain boundaries during creep deformation. Identifying alloy compositions that raise the γ' solvus without lowering the solidus while forming stable, fine grain boundary precipitates is the key for enhancing high temperature mechanical properties. The measured properties will be discussed in comparison with conventional wrought superalloys.
2:50 PM Invited
A Grain-growth-resistant High-entropy Alloy for Forging Applications: Zhi Tang1; Chuan Zhang2; Oleg Senkov3; Jonathan Poplawsky4; Fan Zhang2; Michael Gao5; Peter Liaw6; 1University of Tennessee; Arconic Engines; 2CompuTherm LLC; 3Air Force Research Laboratory; 4Oak Ridge National Laboratory; 5National Energy Technology Laboratory; 6University of Tennessee
We introduce a simple but breakthrough concept to achieve fine grains resistant to grain growth for the first time, demonstrated by three high-entropy alloys (HEA). Microstructures of the three HEAs are revealed by XRD, EBSD and APT to explain why the grain size of one alloy has 10 times finer than the other two alloys, and one order of magnitude slower grain growth at long term exposure at a near melting-point temperature. Similar published HEAs and other conventional alloys are summarized and compared for grain size and grain growth. Then a high throughput calculation by CALPHAD is applied to expand from three alloys to a new type of alloys with thousands of possibilities. The authors believe that this new type of alloy design concept can help the HEA community to find more applications in rings, disks, and forgings industry.
3:10 PM Invited
Metastability Engineering in Aged Non-equiatomic High Entropy Alloys with Heterogenous Structure Towards Superior Strength-ductility Synergy: Cheng Zhang1; Chaoyi Zhu2; Xin Wang1; Fan Ye1; Kevin Kaufman2; Penghui Cao1; Xiaoqing Pan1; Julie Schoenung1; Kenneth Vecchio2; Enrique Lavernia1; 1Department of Materials Science and Engineering, University of California Irvine; 2University of California San Diego
A new class of aged non-equiatomic FeNiCoAl-based high entropy alloys with heterogeneous structure is introduced, which exhibits superior mechanical properties through metastability engineering. In the current alloy system, the formation of B2 (NiAl) particles along high-angle grain boundaries promotes the nucleation of a martensite phase. In addition, stress-induced BCT-structure martensite with a high density of nano-scale twins can form, depending on the composition change of the matrix and the precipitation of γ’ nano-scale particles. The formation of stress-induced martensite is the result of metastability engineering through controlling the martensite start temperature and critical stress. The back-stress strengthening mechanism, unique to the deformation of a heterogeneous microstructure, is verified through mechanical testing, EBSD-based GND density analysis, and TEM analysis. This study confirms the existence of back-stress in precipitation-strengthened alloys with heterogeneous structure, which provides a new strengthening strategy for HEAs. This work also expands the domain of metastability engineering in HEAs.
3:30 PM Invited
Manipulating Structures/Properties of Bulk Metallic Glasses and High-entropy Alloys by Severe Plastic Deformation: Koichi Tsuchiya1; 1International Center for Young Scientists; National Institute for Materials Science
Effect of high-pressure torsion deformation on Zr-Cu-Al bulk metallic glass and high-entropy alloys was investigated. HPT deformation of Zr50Cu40Al10 bulk metallic glass led to significant reduction in nano-hardness and elastic modulus. These changes were accompanied by marked increase in relaxation heat and change in PDF profiles; thus interpreted as the results of structural rejuvenation. HPT was also applied to high entropy alloys, such as CrMnFeCoNi and Al0.3CoFeCrNi. It was revealed that the grain refinement to 50 nm occurs only after 1 turn of HPT. Formation of lamellar structures by nano twin or shear bands plays an important role in the grain refinement, which may be typical of very low stacking fault energy alloys.
3:50 PM Invited
Ductility Improvement Methodologies in Metallic Glasses and High Entropy Alloys: Yanfei Gao1; Hongbin Bei1; 1University of Tennessee - Knoxville
A large number of mechanisms limit the ductility of engineering materials, ranging from necking to ductile fracture. Two quintessential examples are addressed in this talk. First, heterogeneities and strain localizations dominate in metallic glasses, which lead to interesting dependence of ductility on structural/thermomechanical inhomogeneities and geometric features such as notches. Second, high entropy alloys allow an unprecedented freedom in alloy design, from which various strengthening mechanism can be superposed and improve the overall mechanical properties. An example will be given on NiCoCr-3W alloys.
4:10 PM Break
4:25 PM Invited
Mechanical Behavior of Additive Manufactured CoCrNi High Entropy Alloy at 298K and 210K: Soo Yeol Lee1; You Sub Kim1; Hobyung Chae1; Wanchuck Woo2; Dong-Kyu Kim3; E-Wen Huang4; Takuro Kawasaki5; Stefanus Harjo5; 1Chungnam National University; 2Korea Atomic Energy Research Institute; 3University of Ulsan; 4National Chiao Tung University; 5Japan Atomic Energy Agency
The strength, ductility, and toughness of metallic alloys are highly dependent on temperature. In this work, a CoCrNi medium high entropy alloy (HEA) was manufactured by 3D printing using a direct energy deposition (DED) method. In-situ neutron diffraction experiments were performed to study the tensile behavior of the 3D printed CoCrNi HEA at 298K and 210K. The entire diffraction patterns monitored during tensile loading enabled us to examine evolution of 1) lattice strains by diffraction peak shift, 2) texture by integrated diffraction peak intensity, and 3) localized microstructure by diffraction peak broadening. In particular, macroscopic stress-strain response, microscopic elastic-plastic deformation, and strain hardening behavior during tensile loading were compared at 298K and 210K. Moreover, the development of grain structure with decreasing temperature is highlighted by the information obtained from peak profile analysis.
4:45 PM Invited
High-throughput Hot-isostatic-pressing Micro-synthesis for Accelerating Studies of High Entropy Alloys: Lei Zhao1; Liang Jiang2; Lixia Yang1; Bin Liu3; Hui Wang1; Haizhou Wang1; 1Central Iron & Steel Research Institute; 2Yantai University; 3Central South University
A high-throughput synthesis method is developed to study the high entropy alloys (HEAs) based on the powder metallurgy sintering approach. A structural container with a honeycomb array of internal housing is firstly made by additive manufacturing, then filled with powder mixture via combinatorial design, degassed and sealed, consolidated by hot-isostatic-pressing (HIP) process, followed with high temperature heat treatment, and finally formed more than 80 bulk HEAs with various chemistry. These combinatorial HEAs contain 13 elements, including Fe, Cr, Co, Ni, Mo, Mn, W, Si, Nb, Ti, Ta, Cu, and Al. There are 18 types of material system among these HEAs. They are characterized by different high-throughput analyzing methods, such as LIBS, micro-XRF, Full-View-Metallography, SEM, micro-XRD and Scanning-Micro-Hardness etc. The effects of chemistry on microstructure and property are studied. This work put forth a new high-throughput HIP micro-synthesis approach for accelerating the design and screening of bulk HEAs and other materials.
5:05 PM Invited
Improvement of Lattice Distortion by Addition of Zr Element in NbTaTiV Refractory High-entropy Alloy: Chanho Lee1; Yi Chou2; George Kim3; Gian Song4; Michael C. Gao5; Ke An6; Chuan Zhang7; Wei Chen3; Jonathan D. Poplawsky6; Yi-Chia Chou2; Peter K. Liaw1; 1University of Tennessee; 2National Chiao Tung University; 3Illinois Institute of Technology; 4Kongju National University; 5National Energy Technology Laboratory; 6Oak Ridge National Laboratory; 7Computherm, LLC
The lattice distortion is the core effect of HEAs to enhance the strength at room as well as high temperatures. The number of constituent elements with various atomic sizes have the identical possibility to occupy at atom positions of a crystal lattice, which induces a severe distortion of the crystalline lattice. Several studies have attempted to quantitatively measure the lattice distortion with increasing the number of alloying elements, using x-ray diffraction (XRD) and neutron diffraction (ND). However, only limited alloy systems have succeeded to demonstrate the correlation between lattice distortion and mechanical properties. In this study, we have systematically investigated the evolution of lattice distortions for Nb-Ta-Ti-V-Zr systems as function of number of additional elements and its effect on mechanical properties, using experimental [atom-probe-tomography (APT at CNMS), transmission-electron microscopy (TEM)] and modeling methods [density-functional- theory (DFT)]. It is found that lattice distortions have a critical role in improving mechanical properties.