Mechanical Response of Materials Investigated through Novel In-situ Experiments and Modeling: Session III
Sponsored by: TMS Structural Materials Division, TMS: Thin Films and Interfaces Committee, TMS: Advanced Characterization, Testing, and Simulation Committee
Program Organizers: Saurabh Puri, VulcanForms Inc; Amit Pandey, Lockheed Martin Space; Dhriti Bhattacharyya, Australian Nuclear Science and Technology Organization; Dongchan Jang, Korea Advanced Institute of Science and Technology; Jagannathan Rajagopalan, Arizona State University; Josh Kacher, Georgia Institute of Technology; Minh-Son Pham, Imperial College London; Robert Wheeler, Microtesting Solutions LLC; Shailendra Joshi, University of Houston

Tuesday 8:30 AM
March 16, 2021
Room: RM 17
Location: TMS2021 Virtual

Session Chair: Minh-Son Pham, Imperial College


8:30 AM  Keynote
Observation of Microstructure Evolution in Pure Copper and Copper-8 wt. % Aluminium Alloy during Deformation: Sandhya Verma1; Prita Pant1; M P Gururajan1; 1Indian Institute of Technology Bombay
    The present investigation is based on the study of microstructural evolution in pure copper (Cu) and copper-8 wt.% aluminium (Cu8Al) alloy at various strain by interrupted micro-tensile tests. X-ray diffraction (XRD) and scanning electron microscopy (SEM) are performed to acquire the initial and final microstructural details of the samples. The microstructural evolution with deformation is analysed using electron backscattered diffraction (EBSD) for both Cu and Cu8Al alloy. We have observed the effect of geometrically necessary dislocation (GND) density inside the grain with varying grain orientation and near grain boundaries as well as twin boundaries. We have noticed that GND values near boundaries does not behave monotonically for Cu and Cu8Al. We have also discussed about various dislocation interaction with grain boundaries and twin boundaries in Cu and Cu8Al. In addition, we have analysed our results in terms of Schmidt factors and grain reference orientation deviation (GROD).

9:10 AM  
Sub-surface Microtensile Testing in Oxidized Equiatomic Alloy NbTiCr: Robert Wheeler1; Todd Butler2; Marc Doran3; Scott Apt3; Melinda Ostendorf3; 1Microtesting Solutions LLC; 2Air Force Research Laboratory; 3UES, Inc.
    The oxidation of metals at elevated temperatures over time often leads to the development of complex subsurface microstructural changes. Near-surface layered structures can develop normal to the inward diffusion of oxygen and nitrogen acting in concert with the outward diffusion of metal species in complex metallic alloys such as NbTiCr. The conversion of microstructure near the metal/atmosphere interface leads to the formation of oxide scales at the outermost layers followed by internally oxidized layers with oxide and metal phase changes and, in turn, modified metallic layers resulting from composition changes driven by layer formation above. We have first fabricated microscale tensile specimens from within discrete layers below the surface of oxidized NbTiCr. We have then measured the tensile properties within each representative layer in order to understand the variation in overall behavior resulting from the dramatic local microstructural transformations.

9:30 AM  
In-situ Micro-tensile Testing of Proton-irradiated HT-9 Steels: Tanvi Ajantiwalay1; Stuart Maloy2; Khalid Hattar3; Assel Aitkaliyeva1; 1University of Florida; 2Los Alamos National Laboratory; 3Sandia National Laboratory
    One of the major issues with ferritic/martensitic steels (such as HT-9) is low-temperature ductility. During the early stages of irradiation (at low doses), the majority of defect evolution occurs. The changes in mechanical properties at this stage, however, have not been explored yet. In this study, the tensile properties of proton-irradiated HT-9 at low doses and room temperature are analyzed at a micron-scale. Micro-scale tensile tests enable observation of deformation behavior and site-specific testing. The extent of irradiation hardening with an increasing level of dose is further investigated. The results show an increase in yield stress with irradiation to a fluence of 1.24×1014 cm-2 followed by a slight decline at 1.24×1016 cm-2. The fracture surfaces for all the deformed specimens are then visualized with the help of live testing videos and scanning electron microscopy.

9:50 AM  
Dislocation Structure in FeCrAl Alloys through Advanced In-situ Microscopy Experiments: Keyou Mao1; Maxim Gussev1; Caleb Massey1; Kinga Unocic1; Yukinori Yamamoto1; Kevin Field2; Philip Edmondson1; 1Oak Ridge National Laboratory; 2University of Michigan
    In-situ mechanical testing and microstructural analysis was used to probe differences in the deformation behavior of an accident tolerant ferritic alloy following neutron irradiation. Body-centered cubic (bcc) crystal structure deformation is dominated by slip behavior on {110}, {112}, and {123} planes controlled by screw dislocation motion. After irradiation, the dislocation structure is affected by high-density defects leading to localized dislocation channeling and strain bursts. This work investigates this irradiation-induced transition in deformation modes in a Fe-13Cr-5Al-2Mo (wt.%) alloy. Loops and Cr-rich α’ precipitates formed in irradiated FeCrAl alloys hinder dislocation movement. In-situ scanning electron microscopic strain experiments were applied at different strain levels, followed by transmission electron microscopy (TEM) characterization of the dislocation relaxation, patterning, density and their interactive slip systems at various locations such as grain boundaries and interior grains. Preliminary results by scanning TEM dispersive X-ray spectroscopy and atom probe tomography suggest the dissociation of α’ precipitation.

10:10 AM  
In-situ Nanomechanics of Ni-based Superalloys and Bond Coating at Room Temperature to 1000C: Sanjit Bhowmick1; Eric Hintsala1; Praveena Manimunda1; Douglas Stauffer1; 1Bruker
    High-strength structural materials such as Ni-based superalloys and diffusion bond coats are widely used in challenging environments with exposure to mechanical fatigue, particle impact, and erosion at elevated temperatures. Diffusion aluminide bond coats are an example of compositionally and microstructurally graded coatings with significant variation in engineered mechanical properties across the cross-section. Nanoindentation and pillar compression, particularly in situ, can be considered as a well-suited technique for measuring the properties of such complex microstructural materials as the deformation volume can be carefully controlled to probe different precipitates and microstructural zones. In this study, an SEM nanomechanical instrument with an integrated high-temperature stage and an active tip heating was used to conduct pillar compression of aluminide bond coating and superalloy substrate at room temperature and up to 1000C.

10:30 AM  
Analysis of Deformation Mechanisms in Advanced FeCrAl Alloy via SEM-EBSD In-situ Testing: Nitish Bibhanshu1; Maxim Gussev1; Caleb Massey1; Kevin Field2; 1Oak Ridge National Laboratory; 2University of Michigan
    The optimization of FeCrAl alloys for use as an accident tolerant fuel cladding requires an understanding of how the complex microstructure dictates the mechanical response in service. In the presented work, we have analyzed the response at the microstructural scale using in-situ the Electron Backscattered Diffraction (EBSD) technique within a scanning electron microscope (SEM) equipped with a tensile stage. The applied load and crosshead displacement were correlated with locally measured strains and microstructural features within the material. Accumulation of the strain in the materials take place on the expense on the local mis-orientation change within the grains and along the grain boundaries. These identifications were carried out for different prior microstructural features that were developed via wrought, warm-rolled, welded, and neutron irradiated FeCrAl variants.

10:50 AM  
MEMS-based In-situ Tensile Experiments Designed to Arrest Catastrophic Failure in Brittle Nanomaterials: Daehyeok Ahn1; Dongchan Jang2; 1Korea Advanced Institute of Science & Technology; 2Korea Advanced Institute of Science & Technology
    Quantitative characterization of mechanical properties of many nano- or micro-scaled materials is of crucial importance for many technological applications. Among various experimental methods, the in-situ nanomechanical tensile testing is of particular significance due to its capability of direct observation of mechanical behavior. Especially, the tensile loading mode enabling the precise displacement control is desirable for brittle nanomaterials that often suffer from the catastrophic failure by mechanical instability. In this study, we developed the MEMS-based nanomechanical tensile device optimized for stable displacement control even in the presence of the rapid reduction of sample stiffness. The MEMS device is designed to stabilize the motion of the actuating rod in the testing equipment via the high stiffness of springs and the large mass of the movable part. To verify the performance of the device, we conducted tensile testing on the pre-notched metallic glass samples and successfully observed fast load drops during crack propagation.

11:10 AM  
In-situ Characterization of the Damage Initiation and Evolution in Sustainable Cellulose-based Cottonid: Ronja Scholz1; Alexander Delp1; Frank Walther1; 1TU Dortmund University
    The usage of environmentally friendly materials based on sustainable resources is nowadays more important than ever, especially in technical applications. Cottonid is based 100% on cellulose, therefore sutainable and due to its excellent properties a promising alternative material in terms of eco-friendliness. Within this study, the deformation and damage behavior of two Cottonid variants, an industrial standard as well as the structurally optimized variant M60Z50, is characterized for the first time using innovative in situ testing techniques. Quasi-static tensile tests were comparatively performed in a scanning electron microscope as well as a microfocus computer tomograph, and the development of defects present in the initial condition of the materials were investigated on surface and in volume. In general, in the elastic region, no visible damage initiation on the surface and a decrease of overall void volume within the gauge length could be detected for Cottonid. When reaching the yield strength, cracks initiate on the surface at critical areas, like pores and microcracks, which propagate and assemble until total loss of structural integrity. Further, in the plastic region, an increase in void volume could be shown in the gauge length until final failure. Compared to an industrial standard, M60Z50 exhibits a clearly lower percentage in overall void volume and shows increased mechanical properties, like yield strength and ultimate tensile strength. The structural optimization of M60Z50 seems to result in a more sufficient bonding of the paper layers during the manufacturing process, which improves the deformation and damage behavior under quasi-static loading.