Deformation and Damage Mechanisms of High Temperature Alloys: Understanding Deformation Behavior & Damage Using Advanced Characterization
Sponsored by: TMS Structural Materials Division, TMS: High Temperature Alloys Committee
Program Organizers: Mark Hardy, Rolls-Royce Plc; Jonathan Cormier, ENSMA - Institut Pprime - UPR CNRS 3346; Jeremy Rame, Naarea; Akane Suzuki, GE Aerospace Research; Jean-Charles Stinville, University of California, Santa Barbara; Paraskevas Kontis, Norwegian University of Science and Technology; Andrew Wessman, University of Arizona

Tuesday 8:00 AM
March 1, 2022
Room: 304B
Location: Anaheim Convention Center

Session Chair: Paraskevas Kontis, Max-Planck-Institut fur Eisenforschung GmbH; Jean Charles Stinville, University of Illinois at Urbana-Champaign

8:00 AM  
Effects of Alloying Elements on Mechanical Properties and Environmental Resistance of Silicide Strengthened Nb-based Alloys: Akane Suzuki1; Chen Shen1; Patrick Brennan1; Scott Oppenheimer1; Bernard Bewlay1; 1GE Research
    Nb-Si-based alloys offer exciting potential for ultra-high temperature gas turbine applications. As a part of DOE ARPA-E ULTIMATE program aiming to develop refractory metal-based alloy – coating systems for turbine blades, GE initiated an effort to design silicide strengthened Nb-based alloys capable to 1300°C. This presentation will discuss initial results on the alloying effects on high temperature strength, environmental resistance and room temperature ductility in Nb-Si-based alloys. Candidate alloy compositions containing relatively high concentrations of period 6 transition metal elements with or without elements for microstructural refinements were identified through CALPHAD and machine learning property modeling. Relationships between alloy chemistry, microstructure and properties will be discussed based on experimental evaluations of properties.

8:20 AM  
Slip Localization and the Prediction of Fatigue Strength of Polycrystalline Alloys: J.C. Stinville1; M.A. Charpagne1; A. Cervellon2; S. Hémery2; F. Wang3; P.G. Callahan4; V. Valle2; T.M. Pollock5; 1University of Illinois Urbana-Champaign; 2Institut Pprime; 3Shanghai Jiao Tong University; 4Naval Research Laboratory; 5University of California Santa Barbara
    With increasing applied stress, metallic materials experience irreversible deformation, manifested in localized slip events that result in unexpected fatigue failure upon repeated cycling. Recent advances in accelerated fatigue testing, in-situ electron microscopy, digital image correlation methods and multi-modal data analysis have been integrated to quantitatively characterize the evolution of these slip events from the earliest stages of cycling at the nanometer scale over large fields of view in relation to material structure. Statistical analyses of slip events for a large collection of materials with face-centered cubic, hexagonal close-packed and body-centered cubic structures have been performed. Relations between the yield and ultimate tensile strength, cyclic fatigue strength and the amplitude and spacing of slip localization events are uncovered. It is observed for the first time that the fatigue strength of fcc, hcp and bcc metallic alloys can be predicted by the amplitude of slip localization during the first cycle of loading.

8:40 AM  
Intra- and Intergranular Deformation Measurement in Polycrystalline Materials at High Temperature Using High-resolution Digital Image Correlation: Damien Texier1; Julien Milanese2; Eric Andrieu3; Marie-Agathe Charpagne4; Jean-Charles Stinville4; 1CNRS - Institut Clément Ader; 2MIDIVAL; 3CIRIMAT - UMR CNRS 5085; 4Materials Science and Engineering, UIUC
    Capturing irreversible deformation in relation to the microstructure is critical to better understand the mechanical properties of polycrystalline materials. High Resolution-Digital Image Correlation (HR-DIC) has emerged as a quantitative and statistical tool to assess the heterogeneity of the deformation as the function of the microstructure. Tensile tests under controlled atmosphere were performed between room temperature and 650°C on two polycrystalline Ni-based superalloys: Alloy718 and René88DT. While similar slip activity was found to develop for both materials at room temperature, intergranular deformation with significant different activity was observed at elevated temperature between both materials. HR-DIC measurements successfully described slip-mediated grain boundary sliding for René88DT while intense strain localization near/at grain boundaries was observed in Alloy718 without the assistance of transgranular slip events. In addition, the intensity of the grain boundary sliding in Alloy718 was found sensitive to the applied strain rate and lead to premature intergranular cracking.

9:00 AM  
NOW ON-DEMAND ONLY – Investigating the High-temperature High-cycle Fatigue Properties of a Novel Fe-Ni-Cr-Al-Ti-based Superalloy: Shivakant Shukla1; Jonathan Poplawsky1; Donovan Leonard1; Michael Lance1; Govindarajan Muralidharan1; 1Oak Ridge National Laboratory
     High-temperature high-cycle fatigue properties of a precipitation strengthened Ni-Fe-Cr-Al-Ti-based superalloy were evaluated at 900 °C using uniaxial fatigue testing in a servo-hydraulic frame. The microstructures before and after the cyclic loading were investigated using the scanning electron microscopy (SEM), electron backscattered diffraction, transmission electron microscopy and atom probe tomography. γ’ size evolution and oxidation after high-temperature fatigue testing were characterized to understand their role in determining fatigue life. Effect of second phases on fatigue crack initiation was evaluated by fractography and EDS analysis. *Research sponsored by the U.S.DOE, Assistant Secretary for Energy Efficiency and Renewable Energy, Office of Vehicle Technologies, Propulsion Materials Program under contract DE-AC05-00OR22725 with UT-Battelle, LLC. APT was conducted at the ORNL’s Center for Nanophase Materials Sciences (CNMS), a U. S. DOE Office of Science User Facility.

9:20 AM  
In Situ Characterisation of the Thermomechanical Deformation Behaviour of Powder Processed Ni-based Superalloys: Frances Synnott1; Lewis Owen1; Howard Stone2; Nicholas Jones2; Paul Mignanelli3; Mark Hardy3; Martin Jackson1; Katerina Christofidou1; 1University of Sheffield; 2The University of Cambridge; 3Rolls-Royce plc
    Polycrystalline Ni-based superalloys are continuously evolving in order to enable improved properties and higher operating temperatures in critical applications in the aerospace industry. Compositional modifications are sought that can improve both the mechanical and environmental performance of new alloys. To understand the relative merits of Ti and Ta co-additions on the deformation of polycrystalline superalloys, three powder-processed alloys with varying Ti:Ta ratios were investigated in situ under tensile loads in the temperature range 600-800◦C using advanced synchrotron X-ray diffraction. The results enabled the quantification of the effect of the co-additions on the lattice misfit, elastic constants, and load partitioning between the γ and γ′ phases as a function of composition and temperature, providing invaluable information on the deformation characteristics of the constituent phases. This work was supported by Rolls-Royce plc, SFI [18/EPSRC-CDT/3584] and the EPSRC [EP/S022635/1]. Data was collected at the Diamond Light Source [EE9270] and the ESRF [ME1344].

9:40 AM Break

10:00 AM  
Stacking Faults in Forged Polycrystalline Ni-based Superalloys in the Fully Heat-treated Condition Prior to Further Deformation: Regina Schluetter1; Mauro Callisti1; Mark Hardy2; Cathie Rae1; 1University Of Cambridge; 2Rolls-Royce plc
    Significant densities of extended stacking faults were found in two forged and fully heat-treated PM Ni-based superalloys. The densities of the faults varied significantly depending on the heat treatment. Stacking faults can not only potentially interact with active deformation processes, but can wrongly be interpreted as deformation features in interrupted mechanical test samples, thus increasing the difficulty of identifying key deformation mechanisms. Conventional, scanning and high-resolution transmission electron microscopy (S/TEM, HR-TEM) were used along with energy dispersive X-ray and electron energy loss spectroscopy. The analysis revealed Co segregation near the faults and locally varying widths. The faults originate from bulk intragranular precipitates and grow during ageing. Fast cooling rates from solution treatment and long ageing times promote their growth. They are thought to be chemically stabilized faults whose growth is promoted by residual stresses. <br> This work was supported by Rolls-Royce plc and the EPSRC under EP/H022309/1, EP/H500375/1 and EP/M005607/1.

10:20 AM  
Local Phase Transformation Strengthening in Ni-based Superalloys and Induction of Alternative Displacive-diffusional Shearing Pathways: Ashton Egan1; Fei Xue2; Gregory Sparks3; Timothy Smith4; Emmanuelle Marquis2; Sammy Tin5; Michael Mills1; 1Ohio State University; 2University of Michigan; 3Air Force Research Laboratory; 4NASA Glenn Research Center; 5University of Arizona
    Planar defects and microtwins dominate the intermediate temperature creep regime of Ni-based superalloys, where processes are controlled by diffusion mediated reordering and segregation. Local Phase Transformation (LPT) along defects strengthens alloys possessing critical ratios of η/χ formers. A new LPT strengthening along microtwin boundaries has recently been shown through Electron Channeling Contrast Imaging (ECCI) and Scanning Transmission Electron Microscopy (STEM) studies. This LPT has led to formation of ordered-HCP “nano-laths” via coupled displacive-diffusional mechanism by which strain alternatively accumulates. Advanced characterization of this process was conducted using STEM and atomic resolution Energy Dispersive X-Ray Spectroscopy (EDS), confirming lattice occupancies. Correlative Atom Probe Tomography (APT), as well as STEM modeling, were used for phase confirmation. Orientation effects of operative shearing mechanisms, LPTs, and lath formation were studied in polycrystal specimens and compared to single crystal results. Understanding these processes will inform multiscale modeling efforts and assist in alloy design.

10:40 AM  
Investigating Deformation Mechanisms in Ni-based Superalloys with Compact γ'- γ" Coprecipitates: Semanti Mukhopadhyay1; Hariharan Sriram1; Richard DiDomizio2; Andrew Detor2; Robert Hayes3; Gopal B. Viswanathan1; Christopher Zenk4; Yunzhi Wang1; Michael Mills1; 1The Ohio State University; 2GE Global Research Center; 3Metals Technology Inc.; 4Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU)
    Compact coprecipitate morphology in IN718 based alloys, consisting of γ'' phase on all {100} faces of cuboidal γ' precipitates, has been shown to possess superior coarsening resistance. Two microstructures consisting of such a coarsening resistant morphology of γ' and γ'' coprecipitates were stabilized in an IN718-variant alloy (IN718-27) through careful control of processing parameters. While one of the microstructures (A) consists of a unimodal distribution of ‘compact’ coprecipitates, another microstructure (B) exhibits secondary compact coprecipitates along with tertiary composite coprecipitates. The microstructures of these alloys were characterized after tensile creep to 0.5% strain, which revealed that two different modes of deformation are active in A and B. Creep-deformed microstructures investigated through advanced characterization techniques (ECCI, DC-STEM, HR-STEM) will be discussed. The findings will be complemented with the microstructural characterization of creep deformed conventionally processed wrought IN718. The experimental observations will be supplemented by results from a microscopic phase-field model.

11:00 AM  
Materials Selection and Structural Design Considerdations for Regeneratively Cooled Rotating Detonation Rocket Engines: Zachary Cordero1; Eric Jorgensen1; 1Massachusetts Institute of Technology
    Pressure gain combustion, particularly in the form of a rotating detonation rocket engine (RDRE), is an attractive power cycle for SWaP-constrained space propulsion applications. One of the largest hurdles to realizing the benefits of an RDRE is designing the combustor for long life in the harsh, high heat flux detonation environment. The focus of this research is on achieving combustor longevity using a regeneratively cooled rocket engine configuration. The interaction between thermo-mechanical stresses from thermal gradients, cooling channel pressurization, and ultrasonic detonative loading is studied in detail. The key insight from this research is that maximizing the operational life of the combustor requires tailoring the combustor geometry and combustor material to avoid resonance with the rotating detonation wave. This is achieved by judicious selection of the combustor wall thickness, cooling channel parameters, and combustor material.