Frontiers in Solidification Science VIII: Additive Manufacturing / Rapid Solidification
Sponsored by: TMS Materials Processing and Manufacturing Division, TMS: Chemistry and Physics of Materials Committee, TMS: Phase Transformations Committee, TMS: Solidification Committee, TMS: Computational Materials Science and Engineering Committee
Program Organizers: Damien Tourret, IMDEA Materials Institute; Amy Clarke, Los Alamos National Laboratory; Ulrike Hecht, Access e.V.; Nana Ofori-Opoku, Canadian Nuclear Laboratories; Melis Serefoglu, Marmara University; Tiberiu Stan, Asml

Wednesday 2:00 PM
March 17, 2021
Room: RM 56
Location: TMS2021 Virtual

Session Chair: Güven Kurtuldu, ETH Zürich; Ulrike Hecht, Access e.V.; Peter Voorhees, Northwestern University; Damien Tourret, IMDEA Materials


2:00 PM  Invited
Morphological Evolution during Solidification: Tiberiu Stan1; Alexander Chadwick1; Kate Elder1; Xianghui Xiao2; Peter Voorhees1; 1Northwestern University; 2Brookhaven National Laboratory
    Understanding the evolution of solidification structures in three dimensions and as a function of time is central to linking materials processing to microstructure and properties. Time-resolved X-ray tomographic measurements of the evolution of dendrites during the transient stages of growth will be presented. The evolution of parameters characterizing the growth dynamics of the dendrite tip as well as the morphology of the dendrite will be presented. There has been a resurgence in interest in rapid solidification processing due to applications in additive manufacturing. A model for solidification in near the limit of absolute interfacial stability or complete solute trapping has been developed that follows the evolution of thousands of grains during additive manufacturing in three dimensions. An advantage of the approach is that it captures the physics of the motion and rotation of the grain-boundary-solid-liquid-interface trijunctions that are responsible for the evolution of the grain morphology.

2:30 PM  
Quantification of the Extent of Disequilibrium at the Solid-liquid Interface during Additive Manufacturing: Prabhakar Pal1; André Phillion1; 1McMaster University
    This study reports recent findings to quantify the degree of disequilibrium at the solid-liquid interface in order to characterize if an additively manufacturing process route exhibits rapid solidification. A numerical model capable of predicting cellular and dendritic growth at low and high velocities is used to model the crystal growth during selective laser melting (SLM) process. The developed model accounts for various undercooling, the variation in the partition coefficient, liquidus slope, and diffusion coefficient at high velocities. By comparing the predicted results with the published experimental data, we attempted to quantify the magnitude of various undercooling and identify the non-equilibrium phenomenon necessary to quantitatively predict or qualitatively capture the growth model and cellular/dendritic spacing during the SLM process.

2:50 PM  
Grain Refinement Mechanisms of A6061-RAM2 Metal Matrix Composite Alloys during Laser Powder Bed-fusion (LPB-F): Chloe Johnson1; G. Becker1; Kamel Fezzaa2; Jonah Klemm-Toole1; Jeremy Iten3; Amy Clarke1; 1Colorado School of Mines; 2Argonne National Laboratory; 3Elementum 3D
    Additive Manufacturing (AM) allows for the production of components with complex features, such as internal cooling channels, opening the door for the use of higher operating temperatures than previously achievable. In addition, aluminum alloys are strong candidates for lightweighting, although current wrought aluminum alloys are unprintable and suffer from solidification defects like hot tearing. This implies a need for aluminum alloys specifically designed for AM. One such alloy, A6061-RAM2, developed by Elementum 3D, utilizes their Reactive Additive Manufacturing (RAM) process to refine the microstructure and prevent hot tearing. This process uses reactant particles added to base 6061 alloy powder feedstock to generate product inoculants via chemical reaction in the melt. While this alloy achieves refined, crack-free microstructures, the grain refinement mechanisms have not been extensively investigated. Using detailed in-situ and ex-situ characterization, this work explores the effects of the RAM process and solidification conditions on grain refinement in A6061-RAM alloys.

3:10 PM  Invited
In Situ Studies of Alloy Solidification Using Dynamic TEM: Joseph McKeown1; 1Lawrence Livermore National Laboratory
    The dynamic transmission electron microscope (DTEM) enables in situ multi-frame image acquisitions (i.e., movies) of rapidly evolving solidification fronts with high spatial and temporal resolutions. Here, work will be presented from laser-induced rapid solidification (RS) experiments in Al-based alloys. RS occurs in numerous manufacturing processes involving metallic alloys, such as laser welding and additive manufacturing (AM), and results in processing conditions that produce non-equilibrium microstructures. DTEM allows direct observation of RS microstructure evolution and measurements of kinetics. The effects of solute species and solidification rate on phase selection and morphology will be presented, with complementary in situ heat treatments to assess thermal stability and ex situ postmortem microstructure evaluation. Understanding microstructural evolution and the characteristics that form under various solidification conditions is essential for the development of multiscale, experimentally informed predictive modeling, highlighted here by solidification simulations that utilize the in situ measurements from DTEM experiments.

3:40 PM  
Rapid Solidification of Polycrystalline Al-Cu with a Quantitative Phase Field Model and In-situ Imaging: Tatu Pinomaa1; Joseph McKeown2; Anssi Laukkanen1; Jörg Wiezorek3; Nikolas Provatas4; 1VTT Technical Research Centre of Finland; 2Lawrence Livermore National Laboratory; 3University of Pittsburgh; 4McGill University
    A quantitative polycrystalline phase field model is used to analyze the solidification in Al-Cu under conditions corresponding to dynamic transmission electron microscopy (DTEM) experiments. The sharp interface limit of the phase field model is set through a recent matched asymptotic analysis to follow the solute trapping kinetics of the Continuous Growth Model. A new vector order parameter formulation is introduced, which allows better control of grain boundary energy and consistent noise-based nucleation. The phase field simulated microstructures are compared to experiments, including time-resolved DTEM images and as-solidified samples. The morphological features of the simulated microstructures agree well with the experiments, and the corresponding simulated concentration profiles are in qualitative agreement with the experimental concentration maps. Combining phase field simulations and DTEM experiments allows one to calibrate hard-to-determine kinetic parameters such as the kinetic coefficient, to validate assumptions related to heat transfer modeling, and to investigate the fundamentals of rapid solidification.

4:00 PM  
Numerical Model of Al-33wt%Cu Eutectic Growth during Impulse Atomization: Jonas Valloton1; Abdoul-Aziz Bogno1; Michel Rappaz2; Hani Henein1; 1University of Alberta; 2Ecole Polytechnique Fédérale de Lausanne
    Rapid solidification of Al-Cu droplets of eutectic composition was carried out using Impulse Atomization. Two distinct morphologies were observed: an irregular undulated eutectic assumed to form during recalescence, followed by a regular lamellar eutectic. The volume fraction of each morphology was measured and nucleation undercooling was deduced using the hypercooling limit. A model of the eutectic solidification was developed assuming that the kinetics of the undulated and regular regions is the same and follows scaling laws established experimentally. The simulated solid fraction forming during recalescence matches the experimental undulated eutectic fraction. Furthermore, the heat balance confirms the adiabatic nature of the solidification during recalescence. Good agreement is found between the model and experimental measurements of lamellar spacing for the regular eutectic. However, the predicted spacing of the undulated zone is much lower than what is observed experimentally. This is attributed to coarsening induced by the latent heat released during recalescence.