High Entropy Alloys IX: Alloy Development and Properties: Joint Session with Materials for High Temperature Applications: Next Generation Superalloys and Beyond
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 8:30 AM
March 17, 2021
Room: RM 10
Location: TMS2021 Virtual
Session Chair: Oleg Senkov, Air Force Research Laboratory; Ridwan Sakidja, Missouri State University
8:30 AM Invited
Temperature Dependent Deformation Behavior and Strengthening Mechanisms in a Two-phase BCC+B2 Refractory High Entropy Alloy: Oleg Senkov1; Jean-Philippe Couzinie2; Satish Rao1; Vishal Soni3; Rajarshi Banerjee3; 1Air Force Research Laboratory; 2Université Paris Est Creteil; 3University of North Texas
Microstructure, room temperature and elevated temperature mechanical properties of a refractory high entropy alloy Al10Nb15Ta5Ti30Zr40 will be reported. The homogenized and continuously cooled (water quenching or air cooling) conditions of this alloy consist of a nanoscale mixture of a disordered BCC and an ordered B2 phases, while subsequent low temperature annealing treatment leads to the formation of additional phases. Despite the multi-phase microstructure, the alloy has excellent room temperature ductility and yield stress of 1050 MPa. With increasing temperature, the yield stress decreases to 852 MPa at 400°C but then increases to 1059 MPa at 600°C. Above 600°C, the yield stress decreases rapidly with increasing temperature becoming 250 MPa at 800°C and less than 50 MPa at 1000°C and 1200°C. Correlations between the mechanical properties and microstructure, as well as temperature-dependent operating strengthening mechanisms, will also be discussed.
8:55 AM Invited
Mechanical Properties of Precipitation Strengthened Refractory High Entropy Alloys at Elevated Temperatures: Stephan Laube1; Steven Schellert2; Daniel Schliephake1; Alexander Kauffmann1; Bronislava Gorr2; Hans-Jürgen Christ2; Martin Heilmaier1; 1Karlsruher Institut für Technologie (KIT); 2Universität Siegen
Solid solution strengthening in A2 or B2 refractory complex concentrated alloys is very likely not sufficient to achieve suitable high-temperature strength and creep resistance for potential high-temperature applications. Strengthening phases need to be introduced by proper alloy design and suitable heat-treatments. A two-phase microstructure with coherent cuboidal precipitates can be stabilized in the AlMoNbTaTiZr system [Senkov et al., JOM (2014)]. However, it is crucial to embed the B2 strengthening phase in an A2 matrix to maintain the ductility of the alloy at lower temperatures. This talk will summarize our recent findings on the development of alloys similar in microstructure within the AlCrMoTaTi system. Thermodynamic calculations assisted the down selection of alloys. These alloys, produced by arc melting and subsequent homogenization heat-treatment, were investigated by transmission electron diffraction and calorimetric techniques. Mechanical properties were characterized by compression tests at elevated temperatures and discussed in the light of the present microstructures.
9:20 AM
Transport Properties of Binary and Entropy-stabilized Diborides: Alin Niraula1; Bikash Timalsina1; Gregory Hilmas2; William Fahrenholtz2; Ridwan Sakidja1; 1Missouri state university; 2Missouri university of Science and technology
Structural diborides like ZrB2 and HfB2 and their entropy-stabilized variants MB2 (M= transition metals) are of great interest for high temperature structural applications due to their high melting point, excellent mechanical strength, high electrical and thermal conductivity and chemical inertness. In this study, we utilized the Density functional theory (DFT) calculation to predict the electron-phonon interactions which include relaxation times, electrical conductivity, and transport properties of binary and entropy-stabilized diborides. Both low temperature behavior of the thermal conductivity mainly due to the phonons and high temperature ones dominated by the electron contributions can be observed. In addition, we systematically evaluated the effect of additives such as Ta and Cr on the thermal properties of the diborides and compared them with the experimental results. The support from the Advanced Manufacturing program from the CMMI Division of NSF (Award No. 1902069) is gratefully acknowledged. We also thank NERSC for the supercomputer support.
9:40 AM Invited
The Design and Characterization of High Entropy Alloys for High Temperature Applications: Kevin Garber1; Bhaskar Majumdar1; 1New Mexico Institute of Mining and Technology
We report our investigation of high entropy alloys (HEA) for use in the range 600 – 900C, for turbine engine applications. The objective was to evaluate whether the high configurational entropy (delta-S) of HEAs would permit high temperature strengths that were competitive with superalloys, while offering a lower density. CALPHAD based alloy design strategy relied on forming a high volume fraction of L12 precipitates in an fcc matrix, while minimizing brittle phases. Screened alloys were arc melted and suction cast into 4 mm diameter rods. High temperature compression tests of the final alloy (delta-S=1.62) revealed yield strength of 935 MPa at 750 C, which is competitive with most superalloys (delta-S≤1.3) and improved on the best high temperature HEA to date. The density was approximately 7.9 gm/cc, giving the alloy specific strength advantage over existing superalloys. TEM revealed important composition trends in the precipitate and matrix phases, and will be discussed.
10:05 AM Invited
Unique Microstructural Evolution and Deformation Behavior of HfNbTaTiZr BCC High Entropy Alloy at Elevated Temperatures: Nobuhiro Tsuji1; Rajeshwar Eleti1; Atul Chokshi2; Akinobu Shibata3; 1Kyoto University; 2Indian Institute of Science; 3National Institute for Materials Science (NIMS)
We carried out a uniaxial compression tests of HfNbTaTiZr high entropy alloy (HEA) having BCC single phase structure at elevated temperatures higher than 1000°C and different strain rates. Unique dynamic recrystallization (DRX) behavior characterized by significant bulging of initial grain boundaries and resultant necklace structures composed of fine DRX grains, which is unusual in BCC metals and alloys, was found. Interesting grain boundary sliding (GBS) in the heterogeneous necklace structures composed of coarse unrecrystallized grains and surrounding fine DRX grains was confirmed.
10:30 AM Invited
Design of Corrosion and Irradiation Resistant Compositionally Complex Alloys Using a High-throughput Platform for Applications in Extreme Environments: Adrien Couet1; Michael Moorehead1; Michael Niezgoda1; Phalgun Nelaturu1; Bonita Goh1; Yafei Wang1; Mediha Karatas1; Chuan Zhang2; Fan Zhang2; Thien Duong3; Santanu Chaudhuri3; Kumar Sridharan1; Dan Thoma1; 1University of Wisconsin-Madison; 2Computherm LLC; 3Argonne National Laboratory
Current state-of-the-art alloys that are used for turbine or high-temperature energy applications, are usually nickel-based (super)alloys. However, the use of these alloys have fundamental limitations such as their melting temperatures, their microstructure instability under irradiation or they limited corrosion resistance. Compositionally Complex Alloys (CCAs) represent a class of alloys that have shown promising properties in extreme environments but their development is limited by the almost limitless compositional and phase space to explore. A comprehensive high-throughput platform has been developed to design CCAs resistant to extreme environment based on CALPHAD thermokinetics modeling, in-situ alloy processing using direct energy deposition additive manufacturing and novel corrosion and irradiation high-throughput testing methods. Examples of this high-throughput platform will be presented including development of NbMoTiTaAlCr CCAs for turbine applications, FeCrMnMoNi CCAs for structural materials in high-temperature molten salt energy systems, and FeCrMnNi and light/heavy refractory CCAs for advanced fast nuclear reactors applications.
10:55 AM
Microstructure and Mechanical Properties of High-entropy Superalloy HESA-3 at Intermediate Temperature: Takuma Saito1; Akira Ishida2; Michinari Yuyama2; Yuji Takata2; Kyoko Kawagishi1; Hideyuki Murakami1; 1National Institute for Materials Science / Waseda University; 2National Institute for Materials Science
Recently, high-entropy superalloys (HESAs) have been proposed for high temperature applications. HESAs possess γ and γ’ two phase structure, identical to that of Ni-based superalloys, while their compositions are quite different. In addition, structure/property relationship of HESAs, have not been investigated. This study focuses on the effect of heat treatment on microstructural changes and resulting mechanical behavior of HESA. Single crystal bars of HESA-3 (Ni-8.9Fe-16.9Co-7.5Cr-0.9Mo-0.5W-10.3Al-5.8Ti-1.2Nb in at.%) having approximately 70 vol.% of γ’ were fabricated. Some heat treatments were conducted for the bars to control the size and shape of the γ’ precipitates, then tensile and tensile creep test were performed at 760 °C. SEM, STEM, and EBSD analyses were performed for microstructural observation. It is confirmed that shape and distribution of γ’ precipitates can be altered, i.e. regular distribution with cubic shape and irregular distribution with spherical shape. Relationship between microstructure and deformation behavior of HESA-3 will be presented.