4th International Congress on 3D Materials Science (3DMS) 2018: Phase Transformations, Particle Coarsening, Grain Growth, and Recrystallization III
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

Wednesday 8:00 AM
June 13, 2018
Room: Store Scene
Location: Kulturværftet (Culture Yard) Conference Center

8:00 AM  Invited
3D Continuum Theory of Defects and Microstructure under Irradiation: Anter El-Azab1; 1Purdue University
    Irradiation drives materials away from equilibrium by creating point defects at densities much higher than their equilibrium concentrations. Defects diffuse and interact in the material, which leads to microstructure changes and dimensional changes. Although these phenomena originate by one and the same process, which is defect generation, they are often modeled separately. We present a unified theoretical framework for defect and microstructure dynamics under irradiation based upon non-equilibrium thermodynamics. This approach is based on the balance principles of mass, momentum and energy, and the use of the second law of thermodynamics. These principles result in the kinetic equations of point defects at the scale of microstructure, the mesoscale heat equation and stress equilibrium equation. The concepts of continuum mechanics are invoked to describe dimensional changes in the irradiated material. The main features of this framework will be presented along with specific examples related to the irradiation response of single crystals.

8:30 AM  
Integrated Imaging in Three Dimensions: The Sum is Greater than the Parts: Ron Keinan1; Hrishikesh Bale2; Nicolas Gueninchault3; Erik Lauridsen3; Ashwin Shahani1; 1University of Michigan; 2Carl Zeiss X-ray Microscopy, Inc.; 3Xnovo Technology ApS
    Recent developments in laboratory-based diffraction contrast tomography (LabDCT) have shown its capability to non-destructively map the 3D morphology and crystallographic orientation in the bulk of a polycrystalline sample. Using a combination of LabDCT and attenuation-based tomography, we present here the first experimental results from the imaging of a polycrystalline silicon sample and demonstrate the application of this integrated approach in obtaining crucial microstructural and grain related crystallographic information. It is anticipated that our integrated approach can be extended to other microstructures that are simultaneously multiphase and polycrystalline.

8:50 AM  
3D Laboratory Diffraction Contrast Tomography Study of Nucleation in Al-1%Si: Jun Sun1; Yubin Zhang2; Nicolas Gueninchault1; Florian Bachmann1; Allan Lyckegaard1; Erik Lauridsen1; Dorte Juul Jensen2; 1Xnovo Technology; 2Technical University of Denmark
    3D methods have opened new avenues for recrystallization studies and revealed that much accepted ‘knowledge’ does not match what is seen in 3D. This work deals with nucleation within multi-phase metals. Numerous electron microscopy studies have investigated effects of parameters such as size and distribution of second-phase particles on particle stimulated nucleation (PSN) and PSN is ‘known’ to be the major nucleation mechanism in many materials. The novel laboratory diffraction contrast tomography (LabDCT) technique allows non-destructive 3D orientation mapping of crystalline materials. In this study, we applied LabDCT to characterize the nuclei in lightly annealed 50% cr Al-1%(wt)Si. The 3D distribution of particles and nuclei are mapped, revealing that the particles are not the major nucleation site. Only Si particles clustered along the prior grain boundaries are observed to be preferential nucleation sites. This result is discussed and orientation relationships between the nuclei and the neighboring deformed matrix are analyzed.

9:10 AM  
Measuring Anisotropic Grain Boundary Mobilities by Bridging 3D Experiments and Simulations: Jin Zhang1; Peter Voorhees2; Henning Poulsen1; 1Technical University of Denmark; 2Northwestern University
    We propose a fitting approach to measure the anisotropic reduced grain boundary mobilities by comparison between time-resolved 3D x-ray experiments and 3D phase-field simulations. The grain growth in pure iron is measured by diffraction contrast tomography (DCT). With one timestep from the experiment as input, the phase-field method is used to simulate the evolution of grain growth. The dissimilarity between experiment and simulation is characterized by a cost function. The values of the reduced mobilities that minimize the cost function are regarded as the physical values of the materials parameters. The fitting approach is formulated as an optimization problem and is solved iteratively. In each optimization iteration, the original optimization problem is approximated by a series of sub-problems, which are solved individually. The fitting approach is demonstrated on synthetic datasets and then applied to the DCT dataset to measure the reduced mobilities as a function of the grain boundary misorientation.

9:30 AM  
Atomistic Simulation and Phase Field Modeling Studies on the Three-Dimensional Growth Pattern Formation of Magnesium Alloy Dendrite: Jinglian Du1; Ang Zhang1; Zhipeng Guo1; Manhong Yang1; Shoumei Xiong1; 1Tsinghua University
    The 3D pattern formation of magnesium alloy dendrite was investigated using phase field simulations in light of an anisotropic function model developed based on the experimental findings and spherical harmonics. The anisotropic parameters involved in the anisotropy function model were quantified via relevant atomistic simulations based on density functional theory and hexagonal lattice structure. It was found that the simulated results of dendritic growth pattern were in good correspondence with the experimental findings on the 3D dendritic morphology with 18-primary-branch of most magnesium alloys, including Mg-Al, Mg-Ba, Mg-Ca, Mg-Y and Mg-Sn. Furthermore, the 3D morphological transition of Mg-Zn alloy dendrite from 18-primary-brach to 12-primary branch observed in experiments is closely related to the growth parameters, such as supercooling, anisotropic strength and partition coefficient. Our investigations provides a pathway to enhance one’s understanding on 3D growth pattern of magnesium alloy dendrite from phenomenological descriptive picture to a more intrinsic predictive way.

9:50 AM Break