Refractory Metals 2023: Compositionally Complex Alloys - Ultimate Plus
Sponsored by: TMS Structural Materials Division, TMS: Refractory Metals & Materials Committee
Program Organizers: Brady Butler, US Army Research Laboratory; Todd Leonhardt, Rhenium Alloys Inc.; Matthew Osborne, Global Advanced Metals; Zachary Levin, Los Alamos National Laboratory
Wednesday 2:00 PM
March 22, 2023
Room: Aqua E
Location: Hilton
Session Chair: Zach Levin, Los Alamos National Laboratory
2:00 PM Invited
Recent Developments in Refractory Complex Concentrated Alloys (RCCAs): Todd Butler1; Tinuade Daboiku1; Oleg Senkov1; Satish Rao1; Samuel Kuhr1; Daniel Miracle1; Christopher Woodward1; Eric Payton1; 1Air Force Research Laboratory
Refractory complex concentrated alloys (RCCAs) exhibit great potential for future use in high temperature, structural applications, that exceed the temperature capability of Ni-base superalloys. Unlike conventional dilute refractory alloys, concentrated refractory alloys have been reported to display unique combinations of high temperature strength and oxidation resistance, amongst other properties. Recent advancements/trends in the understanding and prediction of microstructure, mechanical strength and environmental resistance of RCCAs will be discussed. In addition, a methodology for probing post-oxidation mechanical strength of RCCAs will beincluded. Existing knowledge gaps and future materials design challenges will also be addressed.
2:30 PM
A Structural Signature for Ductility in Chemically Complex Alloys: Prashant Singh1; Raymundo Arroyave2; Duane D. Johnson1; 1Ames Laboratory; 2Texas A&M University
Similar to conventional refractory metal, existing body-centered cubic (bcc) refractory multi-principal element alloys (RMPEAs) lack room-temperature ductility. Local lattice distortions (LLD) – relative to average (x-ray) lattice positions – are generally expected in RMPEAs due to the varying complex chemical environments. We suggest a dimensionless metric to characterize ductility in MPEAs using LLD. With its innate quantum-mechanical origins, ductility is clearly affected by LLD arising from increased charge transfer due to atomic electronegativity differences in each varying environment. To validate, we choose RMPEAs, known as "Senkov alloys", that exhibit a range of ductility-brittleness. Our results permit a quick assessment of ductility to guide the design of more ductile high-temperature RMPEAs, and accelerated materials discovery if combined with machine-learning.
2:50 PM
Building Fundamentals for Data-Driven Discovery of Refractory High Entropy Alloys with Targeted Mechanical Properties via First-principles and Machine Learning: Shun-Li Shang1; Adam Krajewski1; Arindam Debnath1; Shuang Lin1; Wesley Reinhart1; Zi-Kui Liu1; 1Pennsylvania State University
Ocean of data is fundamental to creating a sustainable ecosystem to understand, design, and discover materials. Taking refractory high entropy alloys (RHEA) as an example, we first show data generation and correlation analysis for pure elements, dilute alloys, and concentrated alloys based on data available in the literature and our high-throughput simulations by first-principles and CALPHAD modeling guided by machine learning. Second, we show cloud-based data infrastructures, the Material-Property-Descriptor (MPDD) Database and ULtrahigh Temperature Refractory Alloys (ULTERA) Database, used to store and process data on atomic structures and RHEA. Finally, we demonstrate an application of our data to inversely design the RHEA with properties, e.g., superior fracture toughness, excellent creep resistance, and outstanding tensile strength and hardness. This work not only provides fundamental properties of pure elements and alloys but also creates a toolset for data-driven understanding and discovery of materials, as illustrated with the mechanical properties of RHEA.
3:10 PM
CALPHAD Assessment of Mo-V-W-Nb-Ta High Entropy Alloys with CVM Based, Temperature Dependent Short Range Order Corrections. ULTIMATE: Sayan Samanta1; Axel van de Walle1; Siya Zhu1; Helena Liu1; Hantong Chen1; Chiraag Nataraj1; 1Brown University
A first-principles evaluation of a CALPHAD based thermodynamic model for Mo-V-W-Nb-Ta high entropy alloy (HEA) alloy system has been conducted in this work. Short Range Order (SRO) play an important role in the thermodynamics properties and mechanical behavior of such HEAs. Here we propose a short-ranged Cluster Variation Method (CVM)-based strategy to parametrize a T-dependent SRO correction to free energies calculated with special quasirandom structures (SQS). These thermodynamic functions are incorporated into a CALPHAD model, thus providing a purely first-principles software pipeline to produce thermodynamic databases (TDB). We demonstrate that this SQS+CVM+CALPHAD paradigm systematically improves the computational thermodynamic state-of-the-art while being compliant with high-throughput alloy-design.
3:30 PM
A New Tungsten Alloy for Fusion Reactors: Neal Parkes1; Alexander Knowles1; Chris Hardie1; 1University of Birmingham
Nuclear Fusion offers us the possibility of an abundant supply of energy without the carbon footprint of other technologies. Due to the extreme environment of fusion reactors, tungsten has been identified as one of the leading candidate materials. However, there are major concerns with tungsten’s high DBTT, potential irradiation embrittlement at low temperature, as well as poor oxidation resistance - during loss-of-coolant or air ingress into the reactor.To address these challenges, W-Cr nanostructured alloys are being developed. Controlled thermal heat treatments are used to produce a nanostructured tungsten alloys to improve (1) ductility (2) irradiation damage resistance and (3) accident tolerance. Alloys were produced by powder processing, characterised using electron microscopy and subjected to various physical/mechanical measurements.
3:50 PM Break
4:05 PM Invited
Rhenium Effect on the Microstructure and Mechanical Properties of NbTiZr and TaTiZr Equiatomic Alloys: Oleg Senkov1; Stephane Gorsse2; Robert Wheeler1; Eric Payton1; Daniel Miracle1; 1Air Force Research Laboratory, Materials and Manufacturing Directorate; 2CNRS, Univ. Bordeaux
Microstructure, phase composition and mechanical properties of NbTiZr, TaTiZr, Re0.3NbTiZr and Re0.3TaTiZr are reported. NbTiZr had a single-phase BCC crystal structure while TaTiZr had a Ti- and Zr-rich BCC matrix phase and Ta-rich nano-meter-sized BCC precipitates at volume fractions of 0.49 and 0.51, respectively. Re0.3NbTiZr consisted of a BCC matrix phase and 14% (by volume) Re-rich precipitates with a FCC crystal structure. The microstructure of Re0.3TaTiZr consisted of a Zr-rich BCC matrix phase and coarse, Re and Ta rich, BCC particles. NbTiZr and TaTiZr had room temperature (RT) yield stress of 920 MPa and 1670 MPa, respectively. 10 at.% Re additions increased the RT yield stress to 1220 MPa in Re0.3NbTiZr and 1715 MPa in Re0.3TaTiZr. Re also considerably improved RT ductility of TaTiZr, from about 2% to 9% total compressive strain. The positive strengthening effect from the Re additions was retained at high (800-1200°C) temperatures.
4:35 PM
Impact of Ti and Al on Ordered B2 Formation in Potential High Temperature RCCAs: Jaimie Tiley1; Soumya Nag1; Sriswaroop Dasari2; Li Cheng1; Christopher Fancher1; Raymond Unocic1; Jason Gardener1; Fan Zhang3; Rajarshi Banerjee2; 1Oak Ridge National Laboratory; 2University of North Texas; 3Computherm LLC
Meta-stable and heterogenous structures within refractory complex concentrated alloys (RCCAs) provide creative new strengthening mechanisms for material use within extreme environments. The use of ordered structures and chemical segregation coupled with heterogenous phase nucleation sites produced through processing allows increased tailoring of specific microstructures. This research investigates the impact of Ti and Al additions on the formation of heterogeneous B2 and related ordered structures within a TiAlNbTaZr alloy, including the subsequent impact on mechanical properties. Potential compositions for a new candidate alloys were determined through validated CALPHAD models, arc melted, homogenized at 1300C for 24 hours and tested to evaluate phase evolution. Ternary combinations were used to optimize compositions and assess relative strength from precipitates and possibly B2 phases within a BCC matrix. Samples were evaluated using neutron and X-ray diffraction, atom probe tomography, transmission electron microscopy, and mechanical testing at elevated temperatures.
4:55 PM
Phase Identification in Mo-Si-B-Ti Alloys: Qingshan Dong1; Longfei Liu2; John Perepezko2; Laurence Marks1; 1Northwestern University; 2University of Wisconsin-Madison
Mo-Si-B alloys exhibit an attractive potential for structural application at elevated temperatures. The addition of Ti in the replacement of Mo could decrease the density of the Mo-Si-B alloys while maintaining reasonable properties. Using density density-functional theory (DFT) and transmission electron microscopy (TEM), we studied the phase crystal structure, stability, bulk properties, and influence of Ti on the Mo5Si2B (T2) crystal structure.
5:15 PM
Selection, Processing and Characterization of Cr-containing Multiphase Refractory Complex Concentrated Alloys: Nelson Delfino De Campos Neto1; Benjamin Ellyson1; Todd Butler2; Kester Clarke1; Amy Clarke1; 1Colorado School of Mines; 2Air Force Research Laboratory
For ultrahigh temperature performance and continuous operation above 1200 °C, single phase body centered cubic (BCC) solid solution refractory complex concentrated alloys (RCCAs) are desired. Significant opportunity also exists for multiphase RCCAs designed for short-use and/or expendable environments below 1200 °C. Cr-containing RCCAs can present good mechanical properties, suitable oxidation resistance and perhaps even be compatible with coatings. Depending upon the alloy, these alloys tend to show different phases. For example, CrNb, CrNbTi, and CrNbTaTi alloys containing BCC + Laves (C15) phases have revealed promising mechanical properties and oxidation behaviors up to 1200 °C. Significant opportunity exists to influence the microstructure evolution and properties of multiphase, Cr-containing RCCAs by thermomechanical processing. Here we report on our recent progress in the selection, fabrication, and thermomechanical processing and microstructural characterization of novel Cr-containing RCCAs for high temperature applications.
5:35 PM
Effects of Cr Content, Second Phase Formation and Sintering Temperature on Characteristics of WMoVTiCr Refractory High-entropy Alloys: Chun-Liang Chen1; 1Dong-Hwa University
Refractory high-entropy alloys (RHEAs) are important candidate materials for the design of advanced high-temperature structural materials. In this work, WMoVTiCr RHEAs were synthesized by mechanical alloying. The effect of Cr variation, second phase formation, and sintering temperature on microstructural evolution and mechanical properties of the model alloys were investigated. The results demonstrate that the alloy mainly consists of BCC solid solution phase, Ti-rich oxides, and a trace of a Laves phase. The hardness and compressive strength increase significantly with increasing Cr content, which could be ascribed to the microstructure refinement, solid solution, and oxide dispersion strengthening. Moreover, a lower sintering temperature caused incomplete solid solution, thereby reducing material performance.