Additive Manufacturing of Metals: Applications of Solidification Fundamentals: Special Session for MURI Program
Sponsored by: TMS Materials Processing and Manufacturing Division, TMS: Additive Manufacturing Committee, TMS: Solidification Committee
Program Organizers: Wenda Tan, The University of Michigan; Alex Plotkowski, Oak Ridge National Laboratory; Lang Yuan, University of South Carolina; Lianyi Chen, University of Wisconsin-Madison

Monday 8:30 AM
March 20, 2023
Room: 21
Location: SDCC

Session Chair: Alex Plotkowski, Oak Ridge National Laboratory; Wenda Tan, University of Michigan


8:30 AM  Keynote
Rationalization of Interphase Instabilities during Thermo-Mechanical Gyrations Typical to Metal Additive Manufacturing: Jennifer Wolk1; Zoran Sterjovski2; Simon Ringer3; Sudarsanam Babu4; 1Office of Naval Research; 2Defence Science and Technology Group; 3The University of Sydney; 4University of Tennessee, Knoxville
    Overarching goal of this multidisciplinary research initiative is to address the deficiencies in physical metallurgy of additive manufacturing (AM) of metals and alloys. In specific, the stability of phases, liquid-solid (l/s) interfaces, solid-solid (s/s) interfaces, and their plastic instabilities under thermo-mechanical gyrations typical to that of AM are being studied, using model structural materials such as titanium and nickel base alloys. In the research the following fundamental questions are being addressed: (1) Will there be a local equilibrium at the interfaces with thermal gradient? (2) Are the interface response function theories applicable for multicomponent systems? (3) How does the solid/solid interface move under thermal gradients? In addition to the above questions, plastic instabilities in two phase mixtures need to be described under similar thermo-mechanical gyrations. Research so far has shown that for certain AM boundary conditions the theories of solidification and solid-state transformations need to be modified (MURI-AUSMURI Keynote).

8:50 AM  Cancelled
Decomposition of a CrMnFeCoNi High-entropy Alloy Manufactured via Laser Powder Bed Fusion: Hansheng Chen1; Hao Wang1; Zibin Chen2; Bryan Lim1; Hongwei Liu1; Zhiguang Zhu3; Andrew Breen1; Rongkun Zheng1; Sharon Mui Ling Nai3; Sophie Primig4; Xiaozhou Liao1; Simon Ringer1; 1The University of Sydney; 2The Hong Kong Polytechnic University; 3Singapore Institute of Manufacturing Technology; 4UNSW Sydney
    (MURI and AUSMURI Collaborative Research) Phase instability of laser powder bed fusion CrMnFeCoNi high-entropy alloy requires further exploration. Specifically, it remains unclear whether the matrix face centred cubic (FCC) phase remains stable under severe thermal gradients and stresses during the printing process. Using aberration-corrected scanning transmission electron microscopy and atom probe tomography, we found a combination of three phases: a FCC phase (space group 225: Fm-3m, a = 0.36 nm), a Cr-rich intermetallic sigma phase (space group 136: P42/mnm, a = 0.88 nm, c = 0.45 nm), and a NiMn-rich ordered L10 phase (space group 123: P4/mmm, a = 0.26 nm, c = 0.34 nm). Experimental results suggest the rapid heating and cooling cycles firstly triggered the precipitation of the intermetallic sigma phase, followed by the precipitation of the ordered L10 phase transformation in the matrix FCC phase. These phase transformations were accompanied by the local elemental rearrangement.

9:10 AM  
Estimation of Transient Melt-pool Temperature Distributions Using In-situ X-ray Radiography Images: Rakesh Kamath1; Sudarsanam Suresh Babu1; Hahn Choo1; 1University of Tennessee Knoxville
     Understanding the transient evolution of thermal gradient at (G) and velocity (R) of the liquid-solid and vapor-liquid interfaces is key to obtain desired microstructures in additive manufacturing. In-situ dynamic x-ray radiography has been leveraged in recent years to probe the transient evolution of R with high spatial and temporal resolution. However, the current methods used to measure G are either incapable of sub-melt-pool surface measurement (thermography) or have lower spatial/temporal resolution (x-ray diffraction). In this study, we overcome the above shortcomings by successfully demonstrating a novel approach to estimate the transient, sub-surface temperature distributions from x-ray radiographs of laser melting (spot and raster) events in Ti-6Al-4V alloy. This workflow can be applied to the wealth of existing radiography data to correlate the local solidification microstructure to transient G and R and further aid the validation and improvement of melt-pool simulations.*Supported by MURI and AUSMURI Collaborative Research.

9:30 AM  
In Situ Melt Pool Measurements for Laser Powder Bed Fusion using Multi Sensing and Correlation Analysis: Rongxuan Wang1; David Garcia1; Rakesh Kamath2; Chaoran Dou1; Xiaohan Ma1; Bo Shen1; Choo Hahn2; Kamel Fezzaa3; Hang Z. Yu1; Zhenyu Kong1; 1Virginia Tech; 2University of Tennessee Knoxville; 3X-ray Science Division, Advanced Photon Source, Argonne National Laboratory
    Laser powder bed fusion still suffers from delamination and porosity due to the lack of understanding of melt pool dynamics. Both geometric and thermal sensing with high spatial and temporal resolutions are necessary to study the fundamental melt pool behavior. This work integrates three advanced sensing technologies: synchrotron X-ray imaging, high-speed IR camera, and high-spatial-resolution IR camera to characterize melt pool shape dynamics, keyhole, vapor plume, and thermal evolution in Ti-6Al-4V and 410 stainless steel spot melt cases. Quantifications on boundary velocities, melt pool dimensions, thermal gradients, and cooling rates are performed. The study discovers a strong correlation between the thermal and X-ray data, demonstrating the feasibility of using relatively cheap IR cameras to predict features that currently can only be captured using costly synchrotron X-ray imaging. Such correlation can be used for future thermal-based melt pool control and model validation. (MURI and AUSMURI Collaborative Research)

9:50 AM  
Numerical Simulation of the Phase Transformation Dynamics of γ′ during Electron Beam Powder Bed Fusion of IN738 Ni-based Superalloy: Nana Kwabena Adomako1; Nima Haghdadi1; James Dingle2; Xiaozhou Liao2; Simon Ringer2; Sophie Primig1; 1UNSW Sydney; 2The University of Sydney
    Electron beam powder bed fusion (E-PBF) is an additive manufacturing (AM) process that enables fabrication of high-performance nickel-based superalloys such as IN738 for applications in modern aero-engines. While the γ′ phase is responsible for the excellent high-temperature properties of this alloy, a complete understanding of its evolution during printing is currently lacking as most studies focus on the processability and mechanical properties of the finished product. In this study, we introduce an alternate technique to provide new insights into the dynamic behavior of γ′ during the consecutive deposition E-PBF process. This involves computational simulations with thermo-kinetic and thermal analysis software packages. The thermo-kinetic software (MatCalc) performs numerical precipitation kinetics simulations with input from thermal analysis software (ORNL semi-analytical code), which simulates the multiple E-PBF thermal cycles. A good correlation is observed between simulation and experimental measurements, indicating that the simulation method can help design AM parameters for optimum materials properties.

10:10 AM Break

10:25 AM  
In Situ TEM Observations of Thermally Activated Phenomena under Additive Manufacturing Process Conditions: Sriram Vijayan1; Avantika Gupta1; Carolin Fink1; Joerg Jinschek1; 1The Ohio State University
    Engineering components, fabricated via fusion based additive manufacturing (AM) processes, experience varying spatio-temporal thermal transients in the build process due to the localized high energy delivered by the heat source. The combination of extreme thermal gradients (104 - 106 K/m) and/or rapid thermal cycling (102- 105 K/s) may result in metastable and directional microstructures that significantly affect part performance. In order to tailor the microstructure of AM builds to obtain desired properties in ‘as fabricated’ AM builds, it is necessary to understand the solid-state dynamic processes that govern the microstructural evolution under such extreme thermal conditions. Currently, this information can only be obtained through post-mortem characterization, e.g. by electron microscopy. As a part of the MURI and AUSMURI collaborative research, we performed in-situ electron microscopy studies using a modified heating device to simulate thermal AM conditions to observe the solid-state dynamic processes during phase transformations in Ti-6Al-4V and Haynes 282.

10:45 AM  
3D Characterization of Microstructure Anisotropy along the Build Direction of PBF SB-CoNi-10: James Lamb1; Andrew Polonsky2; Kira Pusch1; Evan Raeker1; Tresa Pollock1; 1University of California Santa Barbara; 2Sandia National Labs
    The expanded design space afforded by additive manufacturing (AM) for high temperature alloys used in the hot section of gas turbine engines has the potential to improve engine efficiency through higher operating temperatures and weight reduction. However, many nickel superalloys used in the hot section of turbine engines are prone to solidification cracking when exposed to the high thermal gradients and solidification velocities inherent to powder bed fusion AM . Here we present 3D characterizations of a CoNi-based superalloy with inherent oxidation resistance that shows low cracking susceptibility during PBF. Using kernel-based techniques including 3D geometrically necessary dislocation calculations, dislocation densities and misorientation accumulation along the build direction will be discussed, as well as their relation to cracks, voids, and other defects. Defect formation mechanisms and the spatial distribution of microstructural anisotropy in printed parts will be examined by leveraging multimodal 3D datasets (MURI and AUSMURI Collaborative Research).

11:05 AM  
Spatially Tailoring Chemistry and Property Variations in Electron Beam Additive Manufacturing Builds through Process Control of Unicomposition Powder: Katie O'Donnell1; Maria Quintana1; Thomas Ales1; Michael Kirka2; Christopher Ledford2; Siddhartha Pathak1; Peter Collins1; 1Iowa State University; 2Oak Ridge National Laboratory
    This talk presents a radical departure from the classical means of spatially controlling composition and properties during additive manufacturing processes. For traditional control of local composition, it is common to introduce different feedstocks, whether different prealloyed powder or elemental blends. This work demonstrates a new method of controlling composition by controlling preferential vaporization of elements, in this case intentionally varying the local aluminum concentration starting with a single Ti-6Al-4V powder feedstock. By modifying the scan strategy used to melt the powder in an electron beam powder bed fusion system, local controlled composition variations of ~1.5 wt% Al and the attending elastic and plastic properties are controlled. Importantly, this control is within the x-y plane, overcoming a traditional limitation of compositional control. The result is a sample in which composition and properties (both elastic and plastic) have been spatially engineered and affected. MURI and AUSMURI Collaborative Research.

11:25 AM  
Validation and Prediction with ECP ExaAM Simulations and MURI Additive Experiments: Sam Reeve1; Rakesh Kamath2; Steven Gagniere3; Raymond Wysmierski2; Garrett Fields2; David Hyde4; Yu Fang3; Yuxing Qiu3; John Coleman1; Gerry Knapp1; Kwitae Chong1; Austin Isner1; Stuart Slattery1; Duan Zhang5; Joseph Teran6; Chenfanfu Jiang3; Hahn Choo2; Jim Belak7; 1Oak Ridge National Laboratory; 2University of Tennesse, Knoxville; 3University of California, Los Angeles; 4Vanderbilt University; 5Los Alamos National Laboratory; 6University of California, Davis; 7Lawrence Livermore National Laboratory
     We highlight the collaborative effort of the ExaAM team within the Exascale Computing Project (ECP) with the UTK Multidisciplinary University Research Initiative (MURI) team, both focused on detailed understanding and improvement of additive manufacturing (AM) through simulation and experiments, respectively. This interaction has primarily consisted of material point method and finite volume direct numerical simulations of Advanced Photon Source (APS) in-situ AM spot melt experiments. The collaboration has enabled validation of the models from experiment, demonstrated predictive capabilities of the models, and informed decisions on new experimental direction. In addition, this talk will discuss initial and planned interactions with the larger ExaAM workflow predicting AM microstructure and properties, as well as the larger MURI effort.Supported by ECP (17-SC-20-SC). MURI and AUSMURI Collaborative Research.

11:45 AM  
Solidification Mapping of Refractory Alloys during Additive Manufacturing: Megan Le Corre1; Jonah Klemm-Toole1; Kester Clarke1; Amy Clarke1; 1Colorado School of Mines
    Additive manufacturing for the production of ultra-high temperature refractory alloys promises to circumvent fabrication challenges associated with traditional manufacturing processes like thermomechanical processing. Given the lack of solidification data for refractory alloys, significant opportunity exists to develop fundamental processing-microstructure relationships for traditional and new refractory multi-principal element alloys (RMPEAs). Here we develop microstructure and solidification maps, whereby solidification velocities and thermal gradients are correlated to laser power, scan speed, and spot size, and microstructure characteristics like morphology and microsegregation. Models used include the Ivantsov Marginal Stability model and the Gaümann modification to the Hunt columnar to equiaxed transition model. Melt pool thermal gradients and solidification velocities were determined using heat transfer models such as Rosenthal model. The solidification maps developed in this work have the potential to accelerate industry adoption and implementation of these alloys. MURI and AUSMURI Collaborative Research.