4th International Congress on 3D Materials Science (3DMS) 2018: Dislocations, Twins, Strain, and Plastic Deformation II
Program Organizers: Hugh Simons, Denmark Technical University; Henning Poulsen, Denmark Technical University; David Rowenhorst, Naval Research Laboratory; Peter Voorhees, Northwestern University; Satoshi Hata, Kyushu Univ; McLean Echlin, UC Santa Barbara

Tuesday 9:10 AM
June 12, 2018
Room: Lille Scene
Location: Kulturværftet (Culture Yard) Conference Center

Session Chair: Robert Suter, Carnegie Mellon University


9:10 AM  Invited
Combining In-situ High-energy X-ray Diffraction Measurements with Finite Element Modeling: Darren Pagan1; Paul Shade2; Joel Bernier3; Armand Beaudoin1; Matthew Miller4; 1Cornell High Energy Synchrotron Source; 2Air Force Research Laboratory, Wright Patterson Air Force Base; 3Lawrence Livermore National Laboratory; 4Sibley School of Mechanical and Aerospace Engineering, Cornell University
    As the use of high-energy diffraction microscopy methods increases, new ways to interface these data with computational models are also becoming increasingly wide spread. The ONR-sponsored In-Situ (Integrated Simulation and X-ray Interrogation Tools and training for micromechanics) center at the Cornell High Energy Synchrotron Source (CHESS) seeks to further bridge experimentally gathered diffraction data and computational models. In this presentation, the results from two projects combining diffraction experiments and modeling will be discussed. In the first, average grain stresses measured in-situ from a Ti-7Al specimen are used to develop and calibrate a new constitutive model that is evaluated using finite element crystal plasticity. The second project combines peak evolution data measured using the very-far field diffraction technique as a copper single crystal deformed in-situ with field dislocation mechanics to understand the stress distributions that develop during the formation of shear bands.

9:40 AM  
The Effect of Helium Implantation on the Deformation Behaviour of Tungsten: X-ray Micro-diffraction & Crystal-plasticity: Suchandrima Das1; Edmund Tarleton1; David Armstrong1; Yevhen Zayachuk1; Wenjun Liu2; Ruqing Xu2; Felix Hofmann1; 1University of Oxford; 2Argonne National Laboratory
    Tungsten is a primary candidate material for plasma-facing armour components in future fusion reactors. Fusion neutron bombardment produces defects in tungsten. Interaction of helium, which is produced by transmutation and also injected from the plasma, with these defects modifies their retention and behaviour. Here we examine the effect of helium-implantation-induced damage on deformation behaviour by comparing spherical nano-indents in unimplanted and helium-implanted regions of the same tungsten single crystal. Helium-implantation increases hardness and causes large pileups. 3D-resolved X-ray micro-diffraction uniquely allows investigation of the complex lattice distortions beneath indents. Ion-implanted material shows reduced lattice rotations and residual strains due to indentation, indicating a more confined plastic zone. These observations suggest that initially helium-induced defects obstructs dislocation motion, but are weakened by the subsequent passage of dislocations, leading to reduced work hardening capacity. Initial progress with capturing these effects using 3D crystal plasticity finite element calculations is presented.

10:00 AM Break

10:30 AM  
Development of Three-dimensional Inhomogeneous Plastic Strain during Cold Rolling in Al-Mg Alloys: Masakazu Kobayashi1; Tomoya Aoba1; Hiromi Miura1; 1Toyohashi University of Technology
    To understand local inhomogeneous deformation during thermo-mechanical processing is very important for understanding and prediction of microstructure development, because localized deformation would be one of key mechanism to control recrystallized texture. In this study, development of inhomogeneous plastic strain in three-dimension had been measured in cold rolled Al-Mg alloys that contain small lead particles, which are marker of local strain measurement, by using synchrotron radiation micro-tomography at BL20XU in Japanese synchrotron radiation facility, SPring-8. After synchrotron radiation experiment, the obtained tomographic images were image processed and analyzed to reproduce three-dimensional plastic strain maps. The strain distributions in different Mg content and rolling ratio were compared with microstructures obtained by SEM/EBSD. The relationship between local deformation evolution and grain microstructure is discussed.

10:50 AM  
Intragranular Orientation Spread in Tensile-deformed Grains in Austenitic Steel: Nicolai Juul1; Jette Oddershede2; Grethe Winther1; 1Technical University of Denmark; 2Xnovotech
    A 0.7x0.7x0.5 mm3 volume of a 316L austenitic stainless steel sample was examined by 3DXRD at CHESS. The sample was subjected to tensile deformation while illuminated during several load steps, resulting in a successful characterisation of the tensile-deformation behaviour of more than 300 grains up to 5% elongation. The focus is on the introduced intragranular orientation spread (mosaicity) of individual grains representatively chosen from the data set. Initially, the volume was illuminated in a near-field detector setup, ensuring an accurate spatial map of the undeformed microstructure, which serves as an ideal input for a simulation of the experiment using the crystal plasticity finite element method. The simulation was analysed and reconstructed in a similar fashion to the experiment, using artificial diffraction software, to analyse the level of agreement with the measured mosaicity. This gives insight into the slip activity of the grains and the governing parameters of the simulated grains.

11:10 AM  
Micromechanical Evolution of Ti-7Al Under Cyclic Loading: Rachel Lim1; Darren Pagan2; Yufeng Shen1; Joel Bernier3; Robert Suter1; Anthony Rollett1; 1Carnegie Mellon University; 2Cornell High Energy Synchrotron Source; 3Lawrence Livermore National Laboratory
    High-energy x-ray diffraction microscopy (HEDM), an in situ, non-destructive, 3D characterization technique, was used to track microstructural evolution in a sample of α-phase Ti-7Al under cyclic tensile loading over the first 200 cycles. Near-field HEDM measures orientation on a regular grid which provides grain morphology, while far-field HEDM measures the strain state of each individual grain. Combined with digital image correlation (DIC), we perform grain-by-grain analysis to track strain evolution. The results show a decrease in residual elastic strain over the first cycle followed by an increasing build-up of strain. There is a broadening in the von Mises stress distribution across increasing cycles and the development of a long tail on the upper end of the distribution. Initially, the hydrostatic stress increases linearly with increasing stress coaxiality angle, and by around cycle 60-70, the trend rotates to decreasing.

11:30 AM  
Assessing Experimental Parameter Space for Achieving Quantitative Electron Tomography for Nanometer-scale Plastic Deformation: Ya-Peng Yu1; Joshua Stuckner1; Chang-Yu Hung1; Hiromitsu Furukawa2; Mitsuhiro Murayama1; 1Virginia Tech; 2System In Frontier, Inc
    Integrating in-situ deformation and electron tomography techniques allows us to visualize the materials’ response to an applied stress in three-dimension with nanometer scale spatial resolution and reducing several well-known artifacts such as the projection effect. On the other hand, implementing deformation mechanism introduces additional experimental constraints, for example, narrower tilt angle range, those could influence the accuracy of three-dimensional reconstruction in a different way. To materialize quantitative and statistically relevant microstructure interpretation by this technique, we evaluated several key parameters and their combinations to characterize their influences on the accuracy of size and morphology reproducibility. Observing morphology changes of nanostructured materials (a nanoporous gold) and defect structure representation in bulk materials were attempted as a model study.

11:50 AM  
Individual Grains Behaviour during Superelastic Tensile Test of a Shape Memory Alloy Using 3DXRD Synchrotron Techniques and Diffraction Contrast Tomography (DCT) : Younes El-Hachi1; Benoit Malard2; Sophie Berveiller1; Jonathan Wright3; Wolfgang Ludwig3; 1Arts et Métiers ParisTech, LEM3; 2CIRIMAT/ENSIACET; 3ESRF
     In superelasticity, the stress-induced transformation from austenite into martensite is observed in shape memory alloy; to predict it, the knowledge of the austenite stress state is required. The austenite stress state depends on its orientation, its grains size, and neighboring grains that induce intergranular stress interactions in the case of polycrystals. In order to better understand the contribution of each factor, two synchrotron techniques have been used to determine the mechanical behavior of hundreds of individual grains of a Cu-Al-Be polycrystal: the DCT gives access to the real 3D microstructure while the strain and stress tensors were determined by the 3DXRD technique. By DCT, the microstructure of the polycrystal was reconstructed. Correlations with 3DXRD results show that grains exhibit quite large stress depending on their orientation, but also their neighboring grains and their position in the specimen. Results are compared and discussed considering all these parameters.