Fatigue in Materials: Fundamentals, Multiscale Characterizations and Computational Modeling: Cyclic Plastic Localization, Crack Nucleation, and Propagation I
Sponsored by: TMS Materials Processing and Manufacturing Division, TMS Structural Materials Division, TMS: Mechanical Behavior of Materials Committee, TMS: Computational Materials Science and Engineering Committee, TMS: Integrated Computational Materials Engineering Committee, TMS: Advanced Characterization, Testing, and Simulation Committee, TMS: Additive Manufacturing Committee
Program Organizers: J.C. Stinville, University of Illinois Urbana-Champaign; Garrett Pataky, Clemson University; Ashley Spear, University of Utah; Antonios Kontsos, Drexel University; Brian Wisner, Ohio University; Orion Kafka, National Institute Of Standards And Technology
Tuesday 2:30 PM
March 21, 2023
Room: Sapphire H
Location: Hilton
Session Chair: J.C. Stinville, University of Illinois at Urbana-Champaign
2:30 PM Invited
Strain Localisation in Engineering Alloys – Quantifying Discrete Shear to Improve Understanding of Plasticity and Crack Initiation: Michael Preuss1; 1Monash University
Plastic deformation in alloys is typically highly localised creating stress concentrations at the microstructural scale that can lead to premature failure. The discrete shear develops into heterogeneous strain patterns, which might depend on microstructural parameters, and which will affect strain hardening and crack initiation. Recent advancements in imaging nano-patterned mechanical test samples in a SEM for high resolution digital image correlation (HRDIC) has opened new possibilities of understanding the impact of alloy chemistry and microstructures on the degree of strain localisation that develops during monotonic or cyclic loading. I will present examples of utilising HRDIC to quantify the effect of alloy chemistry and microstructures on the degree of strain localisation that raises interesting questions related to for example solid solution strengthening. I will also provide an outlook of the direction of travel with the development of fully integrated in-situ SEM systems enabling the automation of the complex imaging/loading procedures.
2:55 PM
Slip Localization, Slip Transfer at Grain Boundaries and Crack Initiation during Fatigue of Solution-hardened Ni-based Superalloys: Ignacio Escobar-Moreno1; Javier Llorca1; 1IMDEA Materials Institute & Technical University of Madrid
Ni-based superalloys are widely used in rotating elements in aircraft engines and their performance is often limited by the nucleation of fatigue cracks. In this investigation, the deformation mechanisms under fully-reversed, strain controlled cyclic deformation were analyzed in two different solution-hardened Ni-based superalloys, Inconel 600 and Hastelloy C276. The grain size and volume fraction of annealing twins was modified by means of heat treatments. The active slip systems were ascertained by means of slip trace analysis in the scanning electron microscope in combination with electron back-scatter diffraction during interrupted fatigue tests at different cyclic strain amplitudes in the low-cycle fatigue regime. In addition, the conditions for slip transfer/blocking at regular grain and twin boundaries were determined as well as the preferent locations for crack nucleation. It was found that damage nucleation often occurred at regular grain boundaries and triple junctions.
3:15 PM
Dwell Fatigue Behavior of a Fine-grain Ni-based Superalloy 718 at High Temperature: From Strain Localization to Crack Initiation: Melanie Bordas-Czaplicki1; Damien Texier2; Jonathan Cormier3; Patrick Villechaise3; Vincent Roué4; 1Ensma - Institut Pprime -Safran Aircraft; 2Institut Clement Ader (ICA) - UMR CNRS 5312, Université de Toulouse, CNRS, INSA, UPS, Mines Albi, ISAE-SUPAERO; 3Institut Pprime - ISAE-ENSMA; 4Safran Aircraft Engines
Previous work on dwell fatigue of Alloy 718 has shown that crack initiation mechanisms are driven by the interaction of intergranular oxidation and the cumulated plastic strain. The aim of this study is to characterize the strain localization at grain boundaries leading to crack initiation. High resolution-digital image correlation (HR-DIC) tests complemented with EBSD characterization were performed in order to understand grain boundary sliding activity during dwell-fatigue tests at 610°C and 1s or 10s hold time. Tests were performed in vacuum and interrupted at the same cumulated plastic strain thanks to real-time macroscopic DIC measurements. The results allow to determine grains boundaries sensitive to preferential oxidation. Finally, the goal of this study was to combine tests with prior oxidation and to determine the interactions between grain boundary strain localization and grain boundary oxidation in dwell fatigue leading to crack initiation.
3:35 PM
Early Stages of Fatigue Crack Initiation in the Cast and Wrought Polycrystalline Nickel-base Superalloy AD730TM: Julien Prouteau1; Patrick Villechaise1; Jonathan Cormier1; Loic Signor1; 1Institut Pprime, ISAE ENSMA, CNRS UPR3346
In polycrystalline nickel-base superalloys, fatigue crack initiation from crystallographic facets is often found to occur within the coarser grains along or near twin boundaries in relation to the plastic slip band activity. The present work focuses on the early stages of fatigue cracks initiation in the polycrystalline nickel base superalloy AD730TM with a model bimodal microstructure chosen for this study. Symmetrical uniaxial tension-compression fatigue tests were performed at room temperature under total strain control. All fracture surfaces analyses showed crystallographic facets. Loading conditions were selected to perform interrupted fatigue tests including the detection and the statistical analysis of crack initiation sites using SEM and EBSD. The first detected cracks were mostly observed in coarse grains clusters in relation with the twin-boundaries. The configurations that favor crack initiation are discussed with the help of some 3D characterizations.
3:55 PM
On the Mechanism of Cyclic Plastic Accumulation in a Polycrystalline Nickel-Based Superalloy.: Rephayah Black1; Patrick Villechaise2; Valéry Vallé2; Jean-Charles Stinville1; 1University of Illinois at Urbana-Champaign; 2Institut PPRIME, Université de Poitiers
As any material is stressed throughout its fatigue lifetime, plastic deformation accumulates, eventually leading to mechanical failure. Understanding the underlying mechanisms at the microstructural scale that lead to failure allows for more well-informed alloys to be engineered. Using advanced tools, such as high-resolution digital image correlation (HR-DIC) and high-resolution electron backscatter diffraction (HR-EBSD), plastic accumulation can be observed as slip events evolve over the course of thousands of cycles across a large region with further correlation with grain-scale lattice rotation. Of particular interest in this study are significant slip localizations and accumulation that occurred along twin boundaries, of which some formed a stress pile-up known as a ‘microvolume.’ These microvolumes give insight into how stress is concentrated in polycrystalline materials at the grain scale and how to engineer more resilient metals.
4:15 PM Break
4:30 PM Invited
From Slip Activity to Fatigue Crack Nucleation at Basal Twist Grain Boundaries in Titanium Alloys: Cyril Lavogiez1; Patrick Villechaise1; Jean-Charles Stinville2; Fulin Wang3; Marie-Agathe Charpagne2; Meghan Emigh3; Tresa Pollock3; Valery Valle1; Samuel Hemery4; 1Institut Pprime; 2UIUC; 3UCSB; 4Institute Prime - Ensma
Titanium alloys are widely employed in the aerospace industry. The operation of aircrafts implies that components are generally subjected to cyclic mechanical loadings. Accurate fatigue lifetime prediction capabilities are then needed. Significant progress in this direction are offered by microstructure sensitive modeling approaches, which rely on the identification of the underlying mechanisms. In this presentation, a few examples of microstructural configurations associated with crack nucleation will be given to assess the influence of loading conditions, alloy composition and microstructural features. Details of the elementary processes involved in crack nucleation will then be presented. Investigations were carried out using in-situ tensile testing combined with high resolution DIC, EBSD and TEM. This approach enabled to identify specific features exhibited by basal twist grain boundaries to be candidates for crack nucleation. The transition from localized plasticity to crack formation at these microstructural configurations will finally be discussed in light of these results.
4:55 PM
In-site Characterisation of Load Shedding in Macrozones during Dwell Fatigue in Ti-64 Alloy: Yu Cao1; Yang Liu1; Fionn Dunne1; 1Imperial College London
Cold dwell fatigue is a key failure mechanism in the titanium alloys which considerably reduces life span. An important factor potentially influencing the susceptibility to dwell fatigue is the duration of the dwell time and its role in load shedding. This study addresses in-situ high-resolution (optical) DIC characterisation of strain and resulting intragranular stress redistribution within macrozones taking place during stress dwell-loading in three-point beam tests. Stresses are estimated from knowledge of measured strains both during the stress hold and at the unloaded state. Hence spatially resolved creep and stress redistribution within Ti-64 hard and soft macrozones have been quantified during dwell showing experimentally for the first time the explicit redistribution of stress onto grains badly orientated for slip. In addition, it has been possible to quantify the time constant associated with the redistribution in this alloy, which is compared with the results of a theoretical approach, facilitating comparison with other important Ti alloys.
5:15 PM Cancelled
Role of Microstructural Constituents on Deformation under Monotonic Tensile Strain of Additively Manufactured Ni-Al Bronze: Veronika Mazanova1; Jean-Charles Stinville2; Aeriel Leonard1; 1Ohio State University; 2University of Illinois Urbana-Champaign
Ni-Al bronze is widely used in marine applications due to combination of good mechanical properties and corrosion resistance. Recent studies showed that the mechanical properties of this material system can be further enhanced by using WAAM additive manufacturing (AM). However, there is still a knowledge gap in understanding of the effect of the AM microstructure on the deformation mechanisms, especially strain localization. Our work focuses on the detailed multi-scale characterization of the WAAM processed Ni-Al bronze in relation to monotonic tensile properties. As-deposited microstructure is studied as well as that after deformation combining SEM-SE, BSE, FIB, EBSD techniques with STEM and EDS. Localization of the strain and the crack initiation is studied using high-resolution Heaviside-DIC. Key microstructural aspects and deformation mechanisms are identified and discussed related to the performance of the material.
5:35 PM
Fatigue Crack Initiation in Very High Cycle Fatigue of C103: Madeline Vailhe1; Chris Torbet1; Leah Mills1; Tresa Pollock1; 1University of California, Santa Barbara
C103, a niobium based refractory alloy, is primarily used in aerospace applications for sustained high temperature operating environments, such as aerospace propulsion systems. There is limited knowledge of the performance of this alloy under cyclic loading conditions. We aim to gain a fundamental understanding of how slip events develop in C103 and how they escalate to form fatigue cracks during cyclic loading. Ultrasonic fatigue has been employed to study properties in the very-high cycle fatigue (VHCF) regime. At the low stress amplitudes of VHCF, the initiation process for cracks occupies a large fraction of fatigue life and is thus life controlling. These crack initiation sites are linked to slip localization during cyclic loading and emerge from particular microstructural features. Information on how instabilities form and are connected to crystallographic neighborhood configurations will be presented.
5:55 PM
Crack Nucleation and Propagation in Structural Alloys – Design and Certification Considerations: Michael Gorelik1; 1Federal Aviation Administration
There is a significant body of research work addressing micromechanical and physics-based modeling of fatigue phenomena in structural alloys, as well as their experimental characterization. This research has important practical implications in high-impact industries such as aerospace, medical and nuclear applications. However, in order to realize its full potential, it is important to understand how such modeling and experimental capabilities can support specific design objectives and certification requirements. This presentation will discuss how various elements of the “total life” approach, including crack nucleation, small crack growth and long crack growth, map into design and certification considerations for aviation applications. The intent is to provide scientists typically working in the lower TRL domain with a better understanding of the practical implications of their research from the end-user perspective, including design, qualification and certification of high criticality aircraft and engine components produced using both conventional and advanced manufacturing technologies