Additive Manufacturing: Beyond the Beam III: Beyond the Beam - Fundamental Science to Novel Processes
Sponsored by: TMS Materials Processing and Manufacturing Division, TMS: Powder Materials Committee, TMS: Additive Manufacturing Committee
Program Organizers: Brady Butler, US Army Research Laboratory; Peeyush Nandwana, Oak Ridge National Laboratory; James Paramore, US Army Research Laboratory; Nihan Tuncer, Desktop Metal; Markus Chmielus, University of Pittsburgh; Paul Prichard, Kennametal Inc.

Wednesday 8:30 AM
March 2, 2022
Room: 263B
Location: Anaheim Convention Center

Session Chair: Markus Chmielus, University of Pittsburgh

8:30 AM Introductory Comments

8:35 AM  
Modeling Sintering Processes with Continuum Approaches: Thaddeus Low1; Basil Paudel2; 1Ansys, Inc; 2University of Pittsburgh
    Non-beam additive manufacturing methods (AM) like binder jetting and fused deposition modeling commonly require an additional post-processing sintering step to densify porous parts to a desired level, in order to achieve a certain mechanical strength threshold. Due to the viscous creep of the porous material as it undergoes densification, such AM-built parts commonly experience undesired deformation in the form of warping, shrinkage, frictional drag etc., which are further exaggerated depending on the geometry of the part. This ultimately introduces dimensional variability and uncertainties in the final part. Continuum modeling approaches in sintering may be able to aid in this area via the prediction of final displacements and eventual geometric compensation of the parts. This talk will cover continuum modeling approaches and framework for modeling sintering process and the challenges associated with said approaches.

8:55 AM  
Atomistic and Mesoscale Modeling of Sintering Kinetics in Solid-state Additive Manufacturing: Fadi Abdeljawad1; Omar Hussein1; 1Clemson University
    Recently, several solid-state additive manufacturing (AM) techniques have demonstrated the ability to fabricate 3D objects with complex geometries. While such AM techniques differ in their operating principles, sintering of powder compacts is a key aspect of the AM process. Herein, atomistic simulations are used to examine at a fundamental level the role of grain boundary (GB) anisotropy in sintering behavior and densification rates. Simulation results reveal a plethora of densification profiles as a function of GB character. Then, we present a mesoscale phase field model of solid-state sintering that is capable of capturing interface thermodynamics and accounting for various mass transport mechanisms. The computational model is used to examine the role of particle size/distribution, interface properties, and mass transport mechanisms in sintering rates. Several statistical and topological metrics are employed to quantify the microstructural evolution and densification rates.

9:15 AM  
Interface Formation during Metal 3D Printing: From Individual Droplets to 3D Parts: Negar Gilani1; Nesma Aboulkhair1; Marco Simonelli1; Ian Ashcroft1; Richard Hague1; 1University of Nottingham
    Drop-on-demand metal jetting is a new exciting fabrication technique for single and multi-metal components at high resolutions that avoids the use of powders or complicated post-processing. However, the full exploitation of this technology is impeded by a lack of understanding of droplets’ morphology after deposition and solidification, the interface formed by such droplets, and microstructure, all of which define the consistency and quality of printed parts. Here, characteristics of micro-droplets deposited through MetalJet were investigated using FIB-SEM, EBSD, and TEM. In parallel, numerical modelling provided insights into phenomena not directly accessible via experimental such as temperature evolution. The research shows that the substrate wetting and thermal properties are influential in setting the morphology of droplets since they define the droplets dynamics and solidification rate, respectively. Furthermore, the bonding mechanism varies depending on the droplet and substrate materials, while the consistency of interfaces is controlled via process parameters such as temperature.

9:35 AM  
Additive Manufacturing Assisted by Subtractive Sintering of Powder Components: Maricruz Carrillo1; Eugene Olevsky1; Geuntak Lee1; Charles Maniere1; 1San Diego State University
    Powder-based 3D printing has been gaining popularity due to its ease of use and versatility. However, many powder-based methods utilize high power lasers which generate thermal shock conditions in metals and are not ideal for ceramics due to their high melting temperature. In this work, a novel approach of producing high density net-shaped prototypes using Subtractive Sintering (SS) and Solvent Jetting (SJ) is developed. Additive Manufacturing combined with Subtractive Sintering (AM-SS) is a process that includes five simple steps and can produce reliable results. As a proof-of-concept, a zirconia dental crown with a density of 97% was fabricated. Microstructure and properties of the fabricated components are analyzed. Advantages of this method include the ability to efficiently fabricate parts using any powder including nano-sized ceramics, the utilization of conventional furnace only to consolidate, and the elimination of the difficult debinding step inherent to most 3D printing methods.

9:55 AM Break

10:15 AM  
In Situ Observation of Melt Pool in Ultrasonic Vibration-assisted Directed Energy Deposition: Salma El-Azab1; Aleksandra Vyatskikh1; Sen Jiang1; Cheng Zhang1; Lorenzo Valdevit1; Enrique Lavernia1; Julie Schoenung1; 1University of California, Irvine
    Despite the advantages of additive manufacturing (AM), defects such as porosity are common in AM-fabricated metal parts. It is therefore critical to adopt techniques that mitigate defects and provide uniform microstructures, improving the mechanical properties of metal AM parts. In arc welding and casting, ultrasonic vibration (UV) has been shown to decrease porosity, promote formation of equiaxed microstructures, and enhance hardness and strength. In this work, we apply in situ UV to directed energy deposition (DED) of metals. To analyze microstructure, porosity, and chemical composition, we employ scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD) and electron backscatter diffraction (EBSD). Additionally, we utilize in situ high-speed video and thermal imaging of the melt pool surface to elucidate the mechanisms governing UV-assisted DED (UV-A DED) during deposition of stainless steel. Our analysis of the high-speed video suggests that UV widens the melt pool and impacts particle-melt pool interactions.