Materials for High Temperature Applications: Next Generation Superalloys and Beyond: Refractory Alloys: Design and Mechanical Properties
Sponsored by: TMS Structural Materials Division, TMS: Refractory Metals Committee
Program Organizers: Govindarajan Muralidharan, Oak Ridge National Laboratory; Martin Heilmaier, KIT Karlsruhe; Benjamin Adam, Oregon State University; Mario Bochiechio, Pratt & Whitney; Katerina Christofidou, University of Sheffield; Eric Lass, University of Tennessee-Knoxville; Jeremy Rame, Naarea; Sallot Pierre, Safran; Akane Suzuki, GE Aerospace Research; Michael Titus, Purdue University
Tuesday 2:00 PM
March 16, 2021
Room: RM 8
Location: TMS2021 Virtual
Session Chair: Martin Heilmaier, KIT Karlsruhe; Benjamin Adam, Oregon State University
2:00 PM Invited
Rapid Screening, Machine Learning, and Multi-objective Optimization for Refractory Alloy Development: Andrew Detor1; Meinolf Sellmann1; Scott Oppenheimer1; Emily Cheng1; James Ruud1; 1GE Research
Alloy development suffers from the curse of dimensionality, particularly in high entropy or complex concentrated systems. In a field that is already regarded as slow and expensive, a new approach is needed to efficiently develop custom alloys for demanding applications. In this work we review a 15 month effort to experimentally screen 400+ new refractory alloys for performance across a range of metrics including strength, ductility, oxidation resistance, high temperature phase stability, and cost. Active machine learning is used to supplement a more traditional metallurgist intuition-driven approach. Multi-objective optimization routines are also employed to direct experiments and develop alloys with the best balance of properties for the intended use. The methods, tools, and approach detailed in this talk demonstrate the practical and accessible benefits machine learning and multi-objective optimization bring to today’s material development challenges.
2:30 PM
Rapid Design of Refractory Multi-principal Element Alloys for High-T Structural Applications: Theory-guided Combinatorial Synthesis and Characterization Approach: Gaoyuan Ouyang1; Prashant Singh1; Ranran Su2; Shalabh Gupta1; John Perepezko2; Jun Cui1; Matthew Kramer1; Duane Johnson1; 1Ames Laboratory (US DOE); 2University of Wisconsin – Madison
Multi-principal element alloys (MPEA) show high promise for next-generation superalloys. By integrating accurate density-functional theory (DFT) theory and high-throughput combinatorial bulk synthesis, characterization, and testing experiments, we scan rapidly MPEA’s large compositional space to down-select alloys with superior mechanical properties and oxidation resistance. Compositions were refined by DFT-based theory that predicts phase stability and mechanical properties for arbitrary MPEAs. Selected samples were then synthesized via combinatorial arc-melting followed by composition and phase verification. Aided by ultrasonic pulse-echo for precise and rapid elastic moduli measurements, we have identified a subset of alloys compositions in the Mo-W-Ta-Ti-Zr system with large moduli (>260 GPa). Oxidation resistance of short-listed samples was improved by adding a self-healing Mo-aluminoborosilica coating, yielding negligible mass change (<2.6 mg/cm2) over 460 cycles (1h/cycle) at 1300°C. Select samples are being tested for creep properties up to 1300°C using our newly designed high-T creep tester via standard small-punch test configuration.
2:50 PM
New Tools for Analysis of Microplasticity in BCC Refractory Metals: Leah Mills1; Jean-Charles Stinville1; Marie-Agathe Charpagne1; Joseph Wendorf1; McLean Echlin1; Valéry Valle2; Paul Dawson3; Daniel Gianola1; Tresa Pollock1; 1University of California Santa Barbara; 2Pprime Institut; 3Cornell University
Predicting the deformation behavior of BCC refractory metals used in structural applications, such as Multi-Principal Element alloys, motivates the fundamental exploration of slip systems at the scale of individual grains over large areas. High resolution digital image correlation (HR-DIC) in the scanning electron microscope has been employed for identification of active slip systems during monotonic loading of pure niobium. Higher-order slip planes are identified in addition to the conventional {110} and {112} planes, as are the unique slip systems. This in-situ technique is paired with Mechanical Metrics (MechMet), a finite element elasticity code, which was enhanced with material-specific elastic properties and the identified higher order slip strengths. The impact of slip on the high-order planes for various instantiated virtual samples is discussed. The onset of microplasticity prior to macroscopic yielding is analyzed with consideration of the strength-to-stiffness metric. The importance of local polycrystalline "neighborhoods" will also be addressed.
3:10 PM
The Creep Performance of Pesting-Resistant Mo-Si-Ti Alloys: Susanne Obert1; Alexander Kauffmann1; Martin Heilmaier1; 1Karlsruhe Institute for Technology
The development of alternative high-temperature materials with advanced high-temperature capability compared to commercially applied Ni-based superalloys is challenged by achieving resistance to both, chemical and mechanical degradation. The first is typically not fulfilled in Mo-Si-based alloys, which suffer from catastrophic oxidation, called ‘pesting’, due to volatilisation of MoO3 at temperatures below 1000 °C. However, novel Mo-Si-Ti alloys were found to exhibit pesting resistance under certain microstructural and chemical conditions. Their oxidation resistance is determined by the interaction of the high Ti-containing Mo solid solution and M5Si3 silicides, which is closely inter-related to a minimum nominal Ti content. Thus, the resistance to loading under creep conditions is pre-defined by the Ti to Mo ratio, which determines the solidus temperature of the alloys. The potential in creep performance is assessed at 1200 °C by (i) maximising the Mo content, (ii) adjusting the microstructural length-scale and (iii) considering strengthening phases like (Mo,Ti)5Si3.
3:30 PM
Effect of Processing Parameters on Molybdenum Weld Microstructures: Noah Kohlhorst1; Govindarajan Muralidharan2; Roger Miller2; Kevin Faraone2; Ji-Cheng Zhao3; 1Ohio State Univerity; 2Oak Ridge National Laboratory (ORNL); 3University of Maryland, Department of Materials Science and Engineering
Molybdenum alloys have a high melting point, good corrosive resistance, and excellent creep resistance and hence there is significant interest in understanding the microstructure and properties of welds. In this work, a series of molybdenum welds were fabricated using Gas Tungsten Arc (GTA) welding with a diversity of welded microstructures obtained. This work will present quantitative results on grain sizes, grain shapes, and grain boundary curvatures as a function of weld processing parameters obtained using a newly developed technique and the implications of these microstructural characteristics on mechanical properties of welds and the adjoining heat-affected zone.*Research sponsored by the United States Department of Energy (DOE) Office of Facilities Management (NE-31) at the Oak Ridge National Laboratory, managed by UT-Battelle, LLC for the U.S. DOE. Support and guidance were provided by Mary McCune of the US DOE. Primary funding was provided by the NASA Science Mission Directorate.
3:50 PM
Creep Testing of Molybdenum: Brandon Kenny1; Jacqueline Foradora2; Alex Xie3; Gary Rozak2; 1Miami University; 2H.C. Starck Solutions Euclid; 3H.C. Starck Solutions Taicang
Resistance to creep deformation is an important characteristic for high-temperature load bearing applications. This work evaluated bending stress state in sheet material for creep testing. These test methods were applied as a screening test for evaluating the creep resistance of sheet molybdenum and Mo alloys against various thermal process conditions. These methodologies could be expanded for evaluating other high-temperature alloys for creep screening tests. Molybdenum is applied in high-temperature application because the retention of strength and elastic modulus in material processing applications. The first stage of the testing is used for evaluating creep resistance of commercial Mo & Mo alloys for application in high-temperature furnaces capabilities. Testing includes cantilever and 3-point bend creep tests for both arc-cast and powder metallurgy Mo at various temperature regimes. Results of the creep tests will show the optimum thermal condition for resistance at different temperature regimes.