Innovations in High Entropy Alloys and Bulk Metallic Glasses: An SMD & FMD Symposium in Honor of Peter K. Liaw: High Entropy Alloys: Mechanical Properties
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 8:00 AM
February 24, 2020
Room: Marina Ballroom G
Location: Marriott Marquis Hotel
Session Chair: Michael Gao, National Energy Technology Lab; E-Wen Huang, National Chiao Tung University
8:00 AM Introductory Comments
8:10 AM Invited
Research on Bulk Metallic Glasses and High Entropy Alloys: Peter Liaw1; 1University of Tennessee
In this presentation, I will briefly highlight the research activities on bulk-metallic glasses (BMG), high-entropy alloys (HEAs), and other structural materials by our group members and collaborators. I am most grateful that many wonderful students and friends have greatly and graciously help and formulate our research activities. It is truly a great pleasure for me to learn from and interact with our students and friends on research, papers and proposal writings. The talk will focus on microstructures and mechanical behavior of BMGs and HEAs, in particular, fatigue and fracture behavior. In-situ neutron and synchrotron diffractions have been used to understand the phase transformation and mechanical behavior. Moreover, theoretical models have been developed to quantify and predict the phase evolution and mechanical performance. We are very grateful for the financial support from the National Science Foundation, Department of Energy, Army Research Office, Industries, Westinghouse, University of Tennessee, etc.
8:35 AM Invited
Structures and Mechanical Properties of Multiphase High-entropy Alloys at Room and Elevated Temperatures: Tao Yang1; Boxuan Cao1; Chain Tsuan Liu1; 1City University of Hong Kong
Recent studies indicate that high-entropy alloys containing multi-phases have excellent strength and ductility at ambient and cryogenic temperatures. The hardening is mainly due to the precipitation of multicomponent L12 phases with nanoscale particle sizes. However, when tested at elevated temperatures, many high entropy alloys show significant reduction of ductility at intermediated temperatures. In some cases, brittle grain boundary fractures have been observed at 600 to 800C, and embrittlement mechanisms are not well studied at the present time. This talk will be focused on the understanding of the ductility reduction based on the formation of brittle B2, D022, σ and µ phases, environmental effects, and intrinsic grain-boundary weakness at elevated temperatures. Furthermore, the potential ways to eliminate the intermediate-embrittlement will be discussed. (This research is support by the Hong Kong GRF Program under the contract number of CityU11202718).
9:00 AM Invited
Element Effects of CoCrFeNi-based High-entropy Alloys on Low-cycle Fatigue: E-Wen Huang1; Che-Wei Tsai2; An-Chou Yeh2; Soo Yeol Lee3; Stefanus Harjo4; Peter Liaw5; Tu-Ngoc Lam1; You-Shiun Chou1; 1National Chiao Tung University; 2National Tsing Hua University; 3Chungnam National University; 4J-PARC Center, Japan Atomic Energy Agency; 5University of Tennessee
Two equal-molar, face-centered-cubic, high-entropy alloy systems are measured by in-situ neutron-diffraction experiments subjected to continuous tension-compression cyclic loading at room temperature. With spallation neutron, the evolutions of multiple diffraction peaks are collected simultaneously in the axial loading direction and radial direction of the cylindrical dog-bone specimen for lattice-strain measurement and peak profile analysis. Recorded temperature variations during fatigue cycles are compared with the thermodynamics-model predictions based on lattice structural changes. The discrepancy between the modeled and measured temperature evolution indicates the evolution of the microstructure during fatigue deformation, which is validated from the microscopic examination.
9:20 AM Invited
High Temperature Strength of Refractory Complex Concentrated Alloys: Oleg Senkov1; Stephane Gorsse2; Daniel Miracle1; 1United States Air Force Research Laboratory; 2Universite de Bordeaux, CNRS
Thermodynamic and mechanical properties of 15 single-phase and 11 multi-phase refractory complex concentrated alloys (RCCAs) are reported and analyzed. Using the CALPHAD approach, phase diagrams for these alloys are calculated to identify the solidus temperatures and volume fractions of secondary phases. Correlations were identified between the strength drops at 1000C and 1200C and the alloy compositions, room temperature properties, melting temperatures and volume fractions of secondary phases. The influence of alloy density on the temperature dependence of specific yield strength was also explored. The conducted analysis suggests that the loss of high-temperature strength of single-phase BCC RCCAs is related to the activation of diffusion-controlled deformation mechanisms and the alloys with higher melting temperature retain their strength to higher temperatures. On the other hand, a rapid decrease in strength of multi-phase RCCAs with increasing temperature above 1000C is due to dissolution of secondary phases and relatively low melting temperature.
9:40 AM Break
9:55 AM Invited
Tensile Behavior of BCC Refractory High-entropy Alloys: Easo George1; 1Oak Ridge National Laboratory
In this talk, the mechanical behavior of BCC high-entropy alloys within the Ti-Zr-Hf-Nb-Ta system will be analyzed and discussed. These are the only refractory BCC high-entropy alloys that are malleable at room temperature. They can therefore be deformation processed and recrystallized to rigorously control microstructure. They are also relatively ductile at room temperature, which allows tensile tests to be performed, for example, as a function of temperature and strain rate. Model pseudo-binaries within this system are tested and their deformation and fracture behavior correlated with chemical composition. The observed effects of chemical composition are rationalized in terms of elementary deformation mechanisms, which in turn depend on fundamental physical and mechanical properties (e.g., melting point, shear modulus) and the thermodynamic driving forces for phase transformations. Research sponsored by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division.
10:15 AM Invited
Mechanical Behavior of Transformative Complex Concentrated Alloys: Rajiv Mishra1; 1University of North Texas
Complex concentrated alloys (CCAs) extend the compositional paradigm shift of high entropy alloys (HEAs) to new microstructural opportunities. CCAs provide opportunities for tunable performance by manipulating deformation mechanisms. Fe-Mn-Co-Cr-Si alloys exhibit potential for a combination of phase transformation and twinning. These alloys give greater flexibility for tailoring transformation-induced plasticity (TRIP) and twinning-induced plasticity (TWIP), which have guided design of next-generation steel alloys over the last 20 years to a new level. For TRIP CCAs, the ductility can be extended to as high as 50% while maintaining a strength exceeding 1 GPa. The Fe-Mn-Co-Cr-Si alloys show extensive gamma (f.c.c.) to epsilon (h.c.p.) phase transformation followed by additional twinning in the epsilon phase. Design of non-equiatomic CCAs provides a vast, and vastly unexplored compositional space for developing new alloys with tunable properties. Key opportunities for enhanced fatigue limit in TRIP CCAs will be presented.
10:35 AM Invited
Slip Avalanches in Amorphous and Crystalline Materials: Karin Dahmen1; 1University of Illinois
A wide range of materials show slip avalanches under slow shear. We discuss model predictions for the effect of a wide range of experimental tuning parameters on the slip statistics in Bulk Metallic Glasses and High Entropy Alloys. The tuning parameters include temperature, geometry, machine stiffness, strain rate among others. The results can be used to predict future response of the materials to deformation. Initial experiments show agreement with the predictions, and the design of future experiments is discussed.
10:55 AM Invited
Portevin-Le Chatelier Mechanism in Face-Centered-Cubic Metals from Low to High Entropy: Che-Wei Tsai1; Chi Lee1; Po-Ting Lin1; Xie Xie2; Shuying Chen2; Robert Carroll3; Michael LeBlanc3; Braden A. W. Brinkman4; Peter Liaw5; Karin Dahmen3; Jien-Wei Yeh1; 1National Tsing Hua University; 2The University of Tennessee-Knoxville; 3University of Illinois at Urbana-Champaign; 4 University of Washington; 5National Tsing Hua University; The University of Tennessee-Knoxville
Portevin–Le Chatelier effect is a serration phenomenon due to diffusing solute atoms during tensile testing on metals, but its detailed mechanisms are not fully clear yet. We use a different approach to find the mechanism by tensile testing on a series of single-phase face-centered-cubic metals: Ni, CoNi, CoFeNi, CoCrFeNi, and CoCrFeMnNi, which range from low entropy to high entropy in terms of the configurational entropy. The results show that serrations occur on stress-strain curves of CoFeNi, CoCrFeNi, and CoCrFeMnNi alloys in their specific temperature and strain-rate regime. From these, we propose and demonstrate a new mechanism of dislocation pinning for the present substitutional alloys and similar substitutional alloys, which involves the in-situ local rearrangement of substitutional solute atoms by dislocation-core diffusion.
11:15 AM Invited
Modeling and Analysis of Serrated Flows in High Entropy Alloys: Past, Present, and Future: Jamieson Brechtl1; Xie Xie2; Shuying Chen3; Chanho Lee3; Yunzhu Shi4; Haoyan Diao5; Zhong Wang6; Yang Ren7; Junwei Qiao6; Peter Liaw3; 1Oak Ridge National Laboratory; 2FCA US LLC; 3University of Tennessee; 4University of Science and Technology Beijing ; 5Kaiser Aluminum; 6Taiyuan University of Technology; 7Argonne National Laboratory
The serrated flow, which is a complex process that results in the inhomogeneous deformation in an alloy, is associated with plastic deformation that can degrade material properties. The current work will give an overview of past and current theorical modeling and analysis techniques. Furthermore, a comparison of analytical results will be compared to the results of in-situ microscopic-characterization experiments. Finally, recommendations for future research directions regarding the characterization of this type of plastic-deformation behavior will be discussed.