Additive Manufacturing: Beyond the Beam III: Beyond the Beam - Student Session
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 2:00 PM
March 2, 2022
Room: 263B
Location: Anaheim Convention Center

Session Chair: Paul Prichard, Kennametal Inc.

2:00 PM Introductory Comments

2:05 PM  
Investigating Process-structure-property Relationships of 17-4 PH Stainless Steel Fabricated via Laser Beam Powder Bed Fusion (LB-PBF), Laser Powder Directed Energy Deposited (LP-DED), and Metal Binder Jetting (MBJ) Methods: Pooriya Nezhadfar1; Benoit Verquin2; Fabien Lefebvre2; Christophe Reynaud2; Maxime Robert2; Paul Gradl3; Shuai Shao1; Nima Shamsaei1; 1Auburn University; 2CETIM; 3NASA Marshall Space Flight Center
    The existing additive manufacturing (AM) methods may induce different thermal histories to the parts due to their corresponding manufacturing characteristics, causing variation in the micro-/defect-structure of the material. Therefore, it is of interest to understand the micro-/defect-structure and mechanical properties (i.e., tensile and fatigue) of materials fabricated via different AM methods. This study aims to investigate process-structure-property relationships of 17-4 PH stainless steel (SS) additively manufactured via laser beam powder bed fusion (LB-PBF), laser powder directed energy deposition (LP-DED), and metal binder jetting (MBJ). The micro-/defect-structure of laser-based AM methods (i.e., LB-PBF and LP-DED) is characterized and compared to MBJ 17-4 PH SS counterparts. Eventually, the tensile behavior and fatigue performance of additively manufactured 17-4 PH SS are evaluated and compared among different AM methods, and the results are discussed with respect to the variations in the micro-/defect-structure.

2:25 PM  
Modeling of Effect of Powder Spreading on Green Body Dimensional Accuracy in Additive Manufacturing by Binder Jetting: Andrii Maximenko1; Ifeanyichukwu Olumor1; A Maidaniuk1; Eugene Olevsky1; 1San Diego State University
    It is shown that Bullet Physics Engine can be used for Discrete Element modeling of powder spreading during additive manufacturing by binder jetting. It is known that, due to technological restrictions, the thickness of deposited layers during binder jetting should not exceed several powder particle diameters making the application of continuum models of powder medium behavior to be problematic. The conducted modeling shows that dilation of the deposited powder and distortion of previously deposited layers depend on amount of powder removed during spreading, on the thicknesses of the deposited layers, and on the dimensions of the manufactured components. An empirical equation describing the distortion strain as a function of powder spreading parameters is suggested as an approximation of the numerical modeling results. The developed model is experimentally validated. As an optimum way of the powder layers’ deposition, a combination of the non-contact and the blade powder spreading approaches is recommended.

2:45 PM  
Topological Toughness in Additively Manufactured Ceramic Architected Materials: Raphael Thiraux1; Alexander Dupuy1; Lorenzo Valdevit1; 1University of California Irvine
    Technical ceramics exhibit exceptional high-temperature mechanical properties, but unfortunately their brittleness and high melting points make it challenging to manufacture geometrically complex structures with sufficient toughness. Additive manufacturing technologies enable the fabrication of large-scale complex-shape artifacts with architected internal topology; when such topology can be arranged at the microscale, this presents an opportunity to control the form and population of defects, thus affecting its strength. Here, we fabricate ceramic micro-architected materials using direct ink writing (DIW) of an alumina nanoparticle-loaded ink, we investigate the microstructure of the sintered structures, to assess their composition, density, grain size and defect population. Finally, we explore the compressive strength of fully dense and cellular ceramics. We find that woodpile architected materials with relative densities in the 0.4 to 0.7 range exhibit higher strength and damage tolerance than fully dense ceramics printed under identical conditions, an intriguing feature that we attribute to topological toughening.

3:05 PM  
Effect of Powder Heat Treatment on Fatigue Performance of Free Standing AA7075 Cold Spray: Christopher Williamson1; Arthur Webb1; James Jordon1; Luke Brewer1; 1The University of Alabama
    In this study, the effect of powder heat treatment on the fatigue performance of freestanding cold sprayed AA7075 was investigated. In particular, depositions of as-atomized, overaged, and solutionized powders were tested in stress controlled fatigue with the solutionized powder exhibiting an increased life across all stress levels as well as exhibiting a higher runout stress, while the two other powder treatments exhibited nearly identical fatigue properties. Post-testing fractography revealed a change in fracture mechanism in all three depositions, where the short crack growth regime was dominated by transparticle crack growth but as the stress intensity increased the crack began preferentially fracturing around prior particle boundaries. The influence of surface intermetallics present on the as-atomized and overaged powder correlated with smaller regions of transparticle growth and earlier crack initiation to shorten the fatigue life compared to the solutionized deposition.

3:25 PM Break

3:45 PM  
Finite Element Analysis of High-strain-rate Deformation: Elizabeth Hodges1; Victor Champagne2; Robert Hyers1; 1University of Massachusetts-Amherst; 2Cold Spray Innovations International
    In cold spray, the presence of jetting has been linked to bonding. However, the origin of the material instability preceding jetting is highly debated. High-speed impact of hyperelastic material shows similar instability. We theorize that the origin of this instability in hyperelastic material is similar to the origin of instability in cold spray particles. In current work, Abaqus Finite Element Analysis software is being used to examine the dependence of this instability on various physical phenomena, including conservation of volume, inertial and shock effects, and strain-rate effects in the impact of a modeled macro-scale hyperelastic particle. This approach allows different physical effects to be evaluated separately and in combination to isolate the key contributors to the instability. Using models to relate the response of a macroscopic particle also opens a novel avenue for experiments on a length and time scale that allows much more detailed measurements.

4:05 PM  
Processing and Characterization of Tantalum Powders for Cold Spray: Griffin Turner1; James Paramore2; Kelvin Xie1; Brady Butler2; 1Texas A&M University; 2DEVCOM - Army Research Laboratory
    Cold spray tantalum feedstock powders were analyzed by gas fusion methods to determine hydrogen content while particle size distributions and morphologies were measured by laser particle size analysis (LPSA) and SEM imaging. Residual hydrogen in the powder leaves the material in a highly brittle state, inhibiting the plastic deformation, thereby improving substrate and interparticle adhesion. Heat treatments and hydrogen analysis were performed on the feedstock powders to measure how specific heat treatments affect the hydrogen content of the powders without sintering or otherwise affecting powder properties. A heat treatment was found that lowered hydrogen levels below ASTM standards, and LPSA confirmed that the heat treatment did not cause a change in powder size which also affirmed the previous method of powder size analysis through SEM micrographs.

4:25 PM  
Material Flow and Microstructure Evolution during Additive Friction Stir Deposition of Aluminum Alloys: Mackenzie Perry1; Hang Yu1; 1Virginia Polytechnic Institute
    Developing an understanding of the synergy between material deformation and the resultant microstructure evolution is imperative for the full implementation of Additive Friction Stir Deposition. In this work, we systematically study the whole deposition via dissimilar cladding along with specific volumes within the deposited layer via embedded tracers printed at varied processing parameters. X-ray computed tomography and electron backscatter diffraction are employed to visualize the complex shape of the deposits and understand the microstructure progression. From dissimilar aluminum depositions, we find significant macroscopic interfacial mixing with unique 3-D features formed on the advancing side. From tracer experiments, there is drastic mesoscopic shape evolution: the initial cylinder shape is expanded to a spiral disc which is further transformed into long, thin ribbons. Significant grain refinement via geometric dynamic recrystallization occurs rapidly after exiting the tool. By analyzing the strain components, we estimate the lower bound for total strain to be ~101.

4:45 PM  
Microstructure Evolution Pathway in Solid-state Additive Manufacturing of Copper: Robert Griffiths1; David Garcia2; Hang Yu1; 1Virginia Polytechnic Institute; 2Pacific Northwest National Laboratory
    Additive friction stir deposition (AFSD) is a solid-state additive manufacturing technique capable of processing a wide range of metal systems. The process boasts high build rates, full density of deposits, and wrought like mechanical properties of deposited material. The latter of these is due to the microstructures produced, which are generally made up of worked, refined grains. While early investigations highlighted key phenomena resulting in the microstructure evolution of AFSD, these failed to completely describe the material conditions during processing from start-to-finish. Here we utilize a stop-action type experiment to “lock-in” microstructures during the AFSD process. Using these locked depositions and electron back scattered diffraction, the microstructure across the material flow path is described. Several unique features are identified, as well as the identification of discrete thermomechanical regimes across the microstructure evolution pathway in AFSD.

5:05 PM Concluding Comments