Advanced Characterization Techniques for Quantifying and Modeling Deformation: Deformation
Sponsored by: TMS Materials Processing and Manufacturing Division, TMS Structural Materials Division, TMS: Shaping and Forming Committee, TMS: Materials Characterization Committee
Program Organizers: Rodney McCabe, Los Alamos National Laboratory; Thomas Bieler, Michigan State University; Marko Knezevic, University of New Hampshire; Irene Beyerlein, University of California, Santa Barbara; Wolfgang Pantleon, Technical University of Denmark; C. Tasan, Massachusetts Institute of Technology; Arul Kumar Mariyappan, Los Alamos National Laboratory
Thursday 8:30 AM
February 27, 2020
Room: Theater A-2
Location: San Diego Convention Ctr
Session Chair: M Arul Kumar, Los Alamos National Laboratory; Rodney McCabe, Los Alamos National Laboratory
8:30 AM
Advanced Analysis of Acoustic Emission Response of the Main Deformation Mechanisms in Mg: Daria Drozdenko1; Jan Bohlen2; Alexei Vinogradov3; Petr Harcuba4; František Chmelík4; Pavel Lukáč4; Patrik Dobroň5; 1Charles University; Nuclear Physics Institute, CAS; 2Helmholtz-Zentrum Geesthacht; 3Norwegian University of Science and Technology - NTNU; 4Charles University; 51 Charles University; 2 Nuclear Physics Institute, CAS
Acoustic emission (AE) is a powerful in-situ technique for revealing the deformation mechanisms in the metals. This method provides integral information from entire volume about the dynamic processes during plastic deformation. In order to obtain a comprehensive set of AE data, Mg single crystals with various crystallographic orientations were uniaxially compressed at room temperature. Further, advanced statistical analysis of the raw AE signal – so called, adaptive sequential k-means (ASK) procedure - was applied for separating the signals from different sources. Investigation is completed by detailed insight into microstructure provided by in-situ SEM observation, preliminary and post-mortem EBSD mapping. Individual mechanisms of deformation and their interference, all with respect to given orientations of Mg single crystals, sample size, and related to specific stages of the deformation curve will be addressed. Obtained results can be applied in further studies of twinning and dislocation processes in polycrystalline Mg alloys.
8:50 AM
4D Integrated X-ray Imaging and Modeling of Nanoscale Dynamics: Mathew Cherukara1; Kiran Sasikumar2; Subramanian Sankaranarayanan1; Ross Harder1; 1Argonne National Laboratory; 2Avant-garde Materials Simulation
Observing the dynamic behavior of materials can reveal insights into the response of materials under non-equilibrium conditions of pressure, temperature and mechanical load. Such insights into materials response under non-equilibrium is essential to design novel materials for catalysis, low-dimensional heat management, piezoelectrics, and other energy applications. However, material response under such conditions is challenging to characterize especially at the nano to mesoscopic spatiotemporal scales. Time-resolved coherent diffraction imaging (CDI) is a unique technique that enables three-dimensional imaging of lattice structure and strain dynamically. In this talk I will present some examples of our recent work on imaging and modeling of phonon transport and lattice dynamics in nanomaterials under a variety of external stimuli. I will highlight the use of experimentally informed models that leverage large-scale computational resources. These experimentally informed models were used to provide information complementary to the imaging experiment, and at spatio-temporal scales inaccessible to the experiment.
9:10 AM
Micromechanical Characterization of Single-crystalline Silicon at Elevated Temperature: Kosuke Takagi1; Yoji Mine1; Jun Fujise2; Bonggyun Ko2; Toshiaki Ono2; Kazuki Takashima1; 1Kumamoto University; 2SUMCO Corporation
Micro-bending tests were performed at a temperature ranging from 300 to 823 K using Si single crystals with different characteristic lengths to investigate the effects of size and temperature on plasticity. Specimens with dimensions of 5‒20×10×50 μm^3 were obtained from an Si (11N purity). At 300‒723 K, a sudden fracture occurred within an initial elastic regime, while the fracture stress decreased with increasing temperature. Cleavages were observed along (111) and (11-1) planes at 300‒723 K. Above 773 K, the specimens were plastically deformed prior to cracking. The yield stress at 823 K increased with decreasing characteristic length, demonstrating a size effect with a power exponent of ~0.3. Transmission electron microscopy of the microstructure deformed at 823 K revealed gliding of dislocations with a Burgers vector of [011] and [-10-1], and the formation of (111) and (11-1) mechanical twins, which suggests that brittle-to-ductile transition occurs between 773 and 823 K.
9:30 AM
Low Strain Grain Boundary Deformation and Damage: Veronica Anghel1; Ramon Martinez1; Cheng Liu1; George Gray III1; 1Los Alamos National Laboratory
The materials-by-design idea is built upon the premise that critical aspects of materials function can be captured in computational environments that includes making, measuring, and modeling materials. Past research efforts have focused on developing constitutive laws and numerical solvers but less attention has been paid to the representation of material microstructure. The mechanisms of deformation and damage nucleation are strongly dependent on material processing and resulting microstructure. This work focuses on the evolution of deformation and damage nucleation in polycrystalline tantalum under tensile loading at low strain, capturing incipient deformation. In-situ digital image correlation and post-mortem electron backscatter diffraction are applied to quantify the evolution of grain boundary deformation in connection to processing. The material response to deformation is discussed in the context of morphological and textural differences between wrought and additively manufactured tantalum, and is tied to microstructural statistics relevant to the development of predictive capabilities.
9:50 AM
Discrete Dislocation Dynamics Investigation of Partial Dislocation interaction with γ’ Precipitates in Nickel- and Cobalt-based Superalloy: Dylan Madisetti1; Jaafar El-Awady1; 1Johns Hopkins University
A three-dimensional discrete partial-dislocation dynamics code is developed and implemented to examine dislocation-precipitate interaction in Ni- and Co-base single crystal superalloys. This work examines the effect on Ni and Co concentration on the different dislocations γ’ precipitate cutting or looping mechanisms. The current simulations account for the energy and mechanisms associated with the formation of anti-phase boundaries (APB) and super-lattice intrinsic (SISF) stacking faults in addition to complex (CSF), super-lattice extrinsic (SESF), and complex extrinsic (CESF) faults. Furthermore the cutting displacement of the precipitate is recorded. With this new approach, the classical cutting/bowing behavior is investigated as a function of alloying concentration, precipitate spacing, precipitate shape, and loading direction. In addition, dislocation build up due to precipitate pinning is simulated and used to propose a dislocation density modification to the order strengthening equation.
10:10 AM Break
10:30 AM
Strain Hardening of Al-Cu Alloys Investigated with In-situ Neutron Diffraction: Brian Milligan1; Dong Ma2; Amit Shyam2; Amy Clarke1; 1Colorado School of Mines; 2Oak Ridge National Laboratory
Cast Al-Cu alloys have long been of interest due to their high strength derived from nano- and micro-scale precipitates. While the effect of precipitate structure on strength has been well characterized, the strain hardening behavior in these alloys is less understood. This work focuses on strain hardening behavior of a commercial Al-Cu alloy with varying heat treatments and microstructure. Transmission electron microscopy was used to study the precipitate structure after aging, and in-situ neutron diffraction was used to study the strain hardening behavior during tensile testing as a function of precipitate structure. Of interest was the transition of precipitate shearing to Orowan looping as a function of precipitate size at the grain scale during strain hardening. A constitutive model describing this transition was developed. The transition was found to not only be dependent on precipitate thickness, but also grain orientation relative to the direction of applied stress.
10:50 AM
Characterization of Transient State Deformation in Chips Produced by Modulation-assisted machining: Indrani Biswas1; James Mann2; Srinivasan Chandrasekar1; Kevin Trumble1; 1Purdue University; 2University of West Florida
Modulation-assisted machining (MAM) incorporates a cutting tool which is modulated in a controlled fashion chipping out discrete particles out of a workpiece. This study is on characterization of Al-6061-T6 chips (fibers) made with MAM. The fibers are highly deformed with strains in the order of 2-4 depending on the modulation frequency. Because of the periodic nature of cutting, deformation occurs in a transient mode which imparts a non-uniform strain on the chip. Nano-indentation showed a 15% variation in the hardness across the chip length. Measurement of strain in the chips and observation of flow lines aid in understanding the role of deformation in controlling the chip shape. Interrupted linear cutting tests were performed to simulate periodic cutting and observe the chip detachment by in-situ imaging. It illustrated that shear failure occurs in the chip prior to completion of the cut leading to breakage of the chips from the workpiece.
11:10 AM
Grain - Scale Mechanical Characterization of Alpha-Titanium Using Spherical Indentation Stress-Strain Protocols: Natalia Millan-Espitia1; Soumya Mohan1; Adam Pilchak2; Surya Kalidindi1; 1Georgia Institute of Technology; 2Air Force Research Laboratory
Recently established spherical indentation stress-strain protocols have established the feasibility of measuring reliably the mechanical responses at different material lengths scales in a broad range of structural alloys. In the present study, we apply these high-throughput protocols on the primary alpha-phase constituents in polycrystalline samples of Ti5-2.5, Ti811, Ti64, Ti6242 and Ti624 to aggregate a large experimental dataset that documents systematically the effects of alpha-phase chemical composition and grain orientation on the measured values of indentation modulus and the indentation yield strength. This dataset is being offered to the materials community to allow further analyses of the effect of chemical composition of the alpha-phase on its intrinsic elastic-plastic properties (e.g., single crystal elastic constants, critical resolved shear strengths). This study clearly establishes the feasibility and tremendous value of spherical indentation stress-strain protocols for documenting the grain-scale anisotropic mechanical responses of different alpha-phase compositions in high-throughput assays.
11:30 AM
The Effects of Defects on the Mechanical Properties of Au Microparticles: Tyler Flanagan1; Oleg Kovalenko2; Eugen Rabkin2; Seok-Woo Lee1; 1University of Connecticut; 2Technion-Israel Institute of Technology
Mechanical properties of Au microparticles obtained by solid-state-dewetting method were characterized by microcompression tests. Our results revealed that Au microparticles with a top diameter larger than 400 nm exhibit a strong size effect in yield strength, while the strength of particles smaller than 400nm reaches saturation and is size-independent. Transmission electron microscopy revealed that the large microparticles contain several dislocations, while in smaller microparticles no dislocations were observed. Particle growth kinetics could be promoted by the presence of dislocations. Also, we discuss the two different size regimes in terms of the source-controlled plasticity model with a theoretical strength limit. Our numerical calculations not only capture the particles behavior observed in the experiment, but also predict the potential effects of sample geometry on the scaling law. This work shows that the microparticles produced by solid-state-dewetting method represent a convenient model system to study dislocation plasticity at small length scales.
11:50 AM
Assessing the Variation in Localized Deformation During Hydrogen Environment-assisted Cracking in Peak-aged Monel K-500: Zachary Harris1; Adam Thompson1; James Burns1; 1University of Virginia
Recent results indicate that the hydrogen environment-assisted cracking (HEAC) resistance of precipitation-hardened Monel K-500 heat-treated to different aging conditions is strongly influenced by the propensity for slip localization. However, mechanistically linking this slip localization behavior with enhanced HEAC susceptibility is complicated by a lack of experiments directly examining the deformation pertinent to the HEAC fracture path. In this study, the deformation proximate to the fracture surface of a peak-aged Monel K-500 specimen that failed due to HEAC is systematically evaluated at known stress intensity (K) values using EBSD to assess local texture, HR-EBSD to evaluate geometrically necessary dislocation (GND) density distributions, and FIB/BF-STEM to directly image deformation structures. Results from this analysis demonstrate clear variations in dislocation patterning and GND density distribution for different grain orientations, despite experiencing similar mechanical driving forces (K), thereby providing insights into the interplay between microstructure, loading, and environment in determining HEAC susceptibility.