Applications of Solidification Fundamentals: Characterization of Solidification Structures I
Sponsored by: TMS Materials Processing and Manufacturing Division, TMS: Solidification Committee
Program Organizers: Andre Phillion, McMaster University; Amber Genau, University of Alabama at Birmingham; Lifeng Zhang, University of Science and Technology Beijing

Monday 8:30 AM
February 27, 2017
Room: 19
Location: San Diego Convention Ctr

Session Chair: Amber Genau, University of Alabama at Birmingham; Melis Serefoglu, Koc University

8:30 AM  Invited
In-situ Imaging of Metallic Alloy Solidification Dynamics for Advanced Manufacturing: Amy Clarke1; Seth Imhoff2; Damien Tourret2; John Gibbs2; James Mertens2; Younggil Song3; Kamel Fezzaa4; James Hunter2; Michelle Espy2; Frank Merrill2; Fesseha Mariam2; Carl Wilde2; Brian Patterson2; Ricardo Lebensohn2; Joseph McKeown5; John Roehling5; Theron Rodgers6; Jonathan Madison6; Paul Gibbs6; Kevin Baldwin2; Alain Karma3; 1Colorado School of Mines; 2Los Alamos National Laboratory; 3Northeastern University; 4Argonne National Laboratory; 5Lawrence Livermore National Laboratory; 6Sandia National Laboratories
    Solidification is critical to processes like casting and additive manufacturing and the manufacture of metallic alloy components we use in our everyday lives. State-of-the-art characterization techniques, now available at U.S. DOE User Facilities and in the laboratory, are not only enabling fundamental studies of metallic alloy solidification dynamics, but also in-operando, in-situ deformation, and manufacturing studies. Here we use x-ray, proton, and electron imaging to study solidification dynamics from the micro-scale to the macro-scale, at times ranging from microseconds to minutes. Our experimental results are used to inform, develop, and validate computational models at the same length and time-scales. Integrating in-situ characterization and modeling will yield the prediction and control of metallic alloy solidification dynamics and the creation of microstructures and properties by design with advanced manufacturing. This work was supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division.

8:50 AM  
4D Synchrotron X-ray Tomography of Dendritic Microstructure Evolution in a Co Based Alloy during Solidification: Mohammed Azeem1; Peter Rockett2; Andre Phillion3; Shyamprasad Karagadde1; Robert Atwood4; Loic Courtois1; Peter Lee1; 1Manchester University; 2Oxford University; 3McMaster University; 4Diamond Light Source
    Although Ni based superalloys have been used in the high-pressure region of gas turbine technology for decades, Co based superalloys are now emerging as a credible alternative. We present an experimental “tool-kit” for the accelerated development of Co-based alloys using a high X-ray contrast Co-based alloy system and a 4D synchrotron X-ray tomographic (3D + time/temperature) imaging methodology for in situ quantification of evolving solidification microstructures. The growth kinetics of FCC α-Co dendrites was examined and compared with previously reported FCC α-Al dendritic growth in the widely explored AlCu system. In order to inform and validate microstructural models (e.g. phase field), we quantify the evolution of key parameters such as primary and secondary arm spacing, specific surface area and fraction solid. Key phenomena, such as competitive growth and coarsening mechanisms are also captured and discussed.

9:10 AM  
Quantifying Dendritic Evolution in Mg Alloys Using In Situ Synchrotron Tomography: Enyu Guo1; André Phillion2; Daniil Kazantsev1; Sansan Shuai3; Tao Jing3; Peter Lee1; 1University of Manchester; 2McMaster University; 3Tsinghua University
    In situ synchrotron X-ray tomography offers a unique tool to quantify microstructural evolution in materials, allowing the kinetics of transformations to be quantified in real time. In this study, the 4D (3D plus time) evolution of α-Mg dendrites in semi-solid Mg-Zn alloys was investigated via fast synchrotron tomography. Isothermal coarsening of Mg primary dendrites was characterized and quantified in the semi-solid state via measuring the evolution of specific surface area and liquid-solid interface curvature. The effect of Zn concentration and the cooling path during the initial solidification on the morphologic evolution and subsequent coarsening was presented and discussed. The results demonstrate the strong influence of alloy composition and semi-solid processing parameters upon final microstructure, and will also act to inform and validate numerical models of microstructural evolution for semi-solid Mg alloys.

9:30 AM  
Using Synchrotron X-ray Radiography to Measure the Statistics of Intermetallic Compound (IMC) Selection and Growth during Solidification: Shikang Feng1; Enzo Liotti1; Andrew Lui1; Sundaram Kumar1; Keyna O'Reilly1; Patrick Grant1; 1University of Oxford
    Synchrotron X-ray radiography and tomography are used increasingly for studying primary phase solidification dynamics. However, in many alloys the primary structure is recrystallized during downstream operations and the secondary intermetallic compounds (IMCs) are controlling the properties of engineering interest, such as toughness. These IMCs are generally anisotropic in morphology and low in volume fraction, making studies of their real-time evolution difficult and obtaining meaningful statistics time-consuming. We present for the first time a technique based on synchrotron X-ray radiography to obtain statistically meaningful data on growth temperature, morphology and velocity of IMCs during directional solidification of model Al-Cu-Fe alloys. The results show robustly effect of Fe concentration, grain refiner and cooling rate on IMC selection, and are validated by post-solidification characterization. The extension of X-ray imaging to other alloys, including multi-component alloys is described, as well as how these insights might be used to develop more tolerant processing approaches.

9:50 AM  
Analytics on Large Microstructure Datasets Using Two Point Statistics: Application to Coarsening Dendritic Solid-Liquid Mixtures: Yue Sun1; Ahmet Cecen2; Surya Kalidindi2; Peter Voorhees1; 1Northwestern University; 2Georgia Institute of Technology
    Understanding microstructural evolution in materials processing is essential in controlling the properties of the final products. The experimental data for microstructural evolution are often three- or four-dimensional (three spatial dimensions and time) in nature. This makes it difficult for direct analysis of large volumes of data. Here we propose a two-point statistical method for analyzing microstructure properties in large and high-dimensional datasets. This method is independent of the morphology of the structure, unlike the commonly used the secondary arm spacing. Using Pearson correlation coefficient and two-point probability distribution, we have obtained the spatial correlation of the interfacial mean curvature and interfacial velocity of an Al-Cu alloy dendritic microstructure undergoing coarsening. From the correlation maps, we obtain the four-fold symmetry of the dendritic microstructure, and quantitative measures of the characteristic lengths of these complicated microstructures.

10:10 AM Break

10:30 AM  
Four Dimensional Real-time Studies of Metal Solidification under External Fields: Wenjia Du1; Chuangnan Wang1; Billy Koe1; Jiawei Mi1; 1University of Hull
    Recently, we used the speciality synchrotron X-ray beamlines housed at the Diamond Light Source, UK and Swiss Light Source, Switzerland to study in-situ the highly transient phase changes phenomena occurred during the metal solidification processes under an electromagnetic field. The ultrafast synchrotron X-ray tomography techniques were used to reveal how exactly electromagnetic pulses alter the growing directions of primary intermetallic phases and the eutectic phases. The huge amount of dataset obtained from the real-time synchrotron X-ray experiments allow the time-evolved 3D phases under the applied external fields to be studied in-situ, revealing many highly dynamic phenomena concerning phase changes and evolution in metal solidification processes that cannot be obtained by the traditional experimental methods, and opening a new era for quantitative solidification and materials processing research.

10:50 AM  
Scandium Effect on Undercooling and Dendrite Morphology of Al–4.5 wt.%Cu Droplets: Jonas Valloton1; Abdoul-Aziz Bogno1; Daniel Auras1; Marie Bedel2; Guillaume Reinhart3; Hani Henein1; 1University of Alberta; 2ENSAM; 3Aix Marseille Univ, CNRS, IM2NP
    Increasing the mechanical properties of the final product is an ongoing challenge in the field of Additive Manufacturing. These properties can be improved through microstructural refinement via rapid solidification as well as through alloying elements addition. In this work, rapid solidification of Al-4.5wt%Cu alloys with minor Sc addition (up to 0.4wt%) is investigated experimentally using two different containerless solidification techniques: Impulse Atomization (IA) and ElectroMagnetic Levitation (EML). Temperature measurements in EML show that addition of Sc decreases both the primary and eutectic undercoolings. This is corroborated by estimated undercoolings for IA droplets based on measured fractions of eutectic and modeling of secondary dendrite arms coarsening. Microtomography analysis of IA droplets reveals a transition from <100> to <111> dendrites as the undercooling increases. While no refinement is observed, the additions of Sc tends to favor the growth of <100> dendrites under similar solidification conditions.

11:10 AM  
Fluid Flow and Its Influence on Crystal Growth Kinetics in Undercooled Melts: Dieter Herlach1; Sven Reutzel1; Sven Binder1; Hailong Peng1; Thomas Voigtmann1; 1Deutsches Zentrum für Luft- und Raumfahrt
    Electromagnetic levitation is applied to undercool metallic drops. The velocity of rapidly advancing dendrites is measured by a High-Speed-Camera. Crystal growth is controlled by heat and mass transport processes, which in turn govern fluid flow motion. Comparative experimental investigations of AlNi alloy in the Earth laboratory and in reduced gravity give evidence that fluid flow enhances the dendrite growth velocity provided the growth velocity is comparable or less than the fluid flow velocity. Using electrostatic levitation in addition it is shown that forced convection triggers a transition from dendrite growth mode to facetted growth mode of Ni2B alloy. Eventually, MD simulations escorting the experimental investigations study the fluid flow effect on crystal growth. The MD simulations confirm the enhancement of crystal growth by fluid flow. But also, they reveal that the hydrodynamics of surface erosion decreases the growth velocity as a function of the shear rate.

11:30 AM  
In-situ Observation of Multiple Equiaxed Dendrite Interaction under Reduced Gravity Conditions: Laszlo Sturz1; Janin Eiken1; Gerhard Zimmermann1; 1Access e.V.
    Equiaxed dendrite solidification has been investigated in-situ and under low-gravity conditions on the sounding-rocket mission MASER-13. Using high-resolution optical microscopy, the three-dimensional microstructural evolution of the equiaxed dendrites in the transparent alloy system neopentylglycol-30wt.-%camphor was recorded. Applying a small temperature gradient and constant cooling-rate to the sheet-like sample, the equiaxed dendrites were nucleating heterogeneously in the bulk liquid, growing and interacting under conditions dominated by chemical diffusion and transient undercooling. Dendrite morphology, multiple dendrite interaction and individual growth kinetics are investigated in detail. Comparison of the observed morphology to numerical calculations using the phase-field method helped to identify the crystallographic orientation of the primary dendrite arm growth direction, which were found to be dominated by <111> crystallographic planes under the present conditions.