2024 Annual International Solid Freeform Fabrication Symposium (SFF Symp 2024): Materials: Metals III
Program Organizers: Joseph Beaman, University of Texas at Austin

Tuesday 1:30 PM
August 13, 2024
Room: 602
Location: Hilton Austin

Session Chair: John Obielodan, University of Wisconsin-Platteville; Ben Fotovvati, Seurat Technologies

1:30 PM
Integrating In-Situ Sensing for Adaptive Control of Powder Deposition to Advance Remanufacturing Processes: Luke Langan¹; Andrea Camacho-Betancourt¹; Mu’ayyad Al-Shrida²; Li-Hsin Yeh²; Chris Orozco³; Carolin Fink³; Wei Zhang³; Beiwen Li²; Jakob Hamilton²; Iris Rivero¹; ¹University of Florida; ²Iowa State University; ³The Ohio State University
    This research elucidates the relationships between critical process parameters and resultant microstructures and tensile strength for the deposition of nickel-base alloys upon low-alloy steel parts using powder-based directed energy deposition (DED). Deposition of nickel-based alloys have shown success in mitigating brittle phase formation in iron-carbon heat-affected zones under specific thermal conditions. Correlating in-situ geometric and thermal data to resultant microstructural outcomes remains difficult. Thus, this research explains relationships between DED processing parameters (laser power, scanning speed, powder mass flow rate) and the resultant properties of the remanufactured alloy, i.e., microstructural characteristics and tensile strength. Simultaneously combining in-situ structure light scanning with thermal imaging allows for correlating the thermal profile of depositions with laser parameters. Initial work points toward a correlation between in-situ and geometrical sensing and grain size outcomes. This study aims to develop intelligent DED processes for the remanufacturing industry by employing in-situ signals to better understand process outcomes.

1:50 PM
Study of Additively Manufactured Tungsten and Tungsten alloys via Laser Based - Directed Energy Deposition Process for High Temperature Applications: Amaranth Karra¹; Aditya Rohan Narra¹; Bryan Webler¹; ¹Carnegie Mellon University
    Although tungsten (W) is known for its brittle nature at room temperature, recent advancements in additive manufacturing saw a surge in pursuing additive manufacturing (AM) of W and W alloys. This examines the microstructure of pure W and W alloys printed via powder feed laser based - directed energy deposition (DED-LB). While microstructure was examined for porosity and cracking, micro-segregation is studied along with studying for high temperature strength properties. Results show how alloying and process parameter selection can lead to reduction in defects during DED-LB of W and its alloys as well as the effects of alloying on cracking

2:10 PM
Crack Growth and Fatigue-life Predictions for Ti-6Al-4V Fabricated via Laser Directed Energy Deposition: Leah Buiter¹; Aref Yadollahi¹; James Newman²; ¹Purdue University Northwest; ²Mississippi State University
    This study examines the fatigue-crack-growth and fatigue-life behavior of Ti-6Al-4V specimens fabricated via laser directed energy deposition (DED-L). The crack-growth-rate data were obtained using standard compact, C(T), specimens and single-edge-notch-bend, SEN(B), specimens. The large-crack growth tests were conducted on C(T) specimens over a wide range of stress ratios and produced crack growth rates from near-threshold to fracture. SEN(B) specimens exhibit crack growth rates comparable to those observed in C(T) specimens in the near-threshold regime. Fatigue tests were conducted on SEN(B) and K_T = 1 dogbone specimens under constant-amplitude loading of R = 0.1. A plasticity-induced crack closure model, FASTRAN, was used to predict the fatigue life based on the size of process-induced defects detected by X-ray CT. The estimation of fatigue life, utilizing the ΔK_eff-rate curve, exhibited a strong correlation with experimental fatigue test results for both the SEN(B) and K_T= 1 specimens.

2:30 PM
Functionally Graded Refractory High Entropy Alloys Fabricated with Directed Energy Deposition for Alloy Development: Michael Juhasz¹; C. Rietema¹; J. Shittu¹; B. Ellyson¹; T. Voisin¹; J. Mckeown¹; ¹Lawrence Livermore National Laboratory
    The astronomical combination space of possible alloys in the high entropy alloy (HEA) domain is daunting. The ability to create and test large swaths through those compositional spaces is an important component to the eventual down-selection of alloys with engineering interest. Laser Powder Directed Energy Deposition (LP-DED) as a manufacturing method is uniquely poised to add significant value to alloy development in the HEA space which is mainly due to DED's easy incorporation of multiple materials. Discussed here is an experimental framework using DED and in-situ alloying of elemental powders for screening of targeted refractory HEA (R-HEA) alloy systems which complements considerable material simulation work already completed. Presented is an investigation of yield strength versus ductility trade-offs in functionally graded samples as a screening tool for R-HEAs. Prepared by LLNL under Contract DE-AC52-07NA27344. Funding: Laboratory directed research and development projects 22-SI-007.

2:50 PM
Residual Stress Evaluation of EB-PBF Produced High Strength Mo-7Re-1HfC Alloy via Neutron Diffraction: Haozhi Zhang¹; Jenny Forrester¹; Christopher Fancher²; Patxi Fernandez-Zelaia²; Chris Ledford²; Tim Horn¹; ¹North Carolina State University; ²Oak Ridge National Laboratory
    Electron beam powder bed fusion (EB-PBF) emerges as a promising additive manufacturing (AM) technology capable of handling refractory alloys with limited ductility, thanks to its elevated build temperatures and tightly controlled vacuum environment. From the composition perspective, alloying of Re in refractory metal has proven to be an effective route to enhance the ductility of the matrix. Furthermore, incorporating high-melting-point dispersion strengtheners has been recognized for increasing the high-temperature strength of otherwise ductile materials. In this context, a customized Mo-7Re-1HfC (wt.%) alloy serves as the raw powder material for EB-PBF fabrication in the present study. The investigation delves into the processing map of this novel material, scrutinizing the corresponding microstructure and process-induced defects through metallurgical and micro-CT analyses. Moreover, the assessment of residual strain along the build direction of the as-fabricated sample is conducted using neutron diffraction, a non-destructive method offering novel insights into process-induced defects.

3:10 PM
Characterizing the use of Low-cost Steelmaking Feedstocks for Refining ElectroSlag Additive Manufacturing (RESAM): Adam Stevens¹; Rangasayee Kannan¹; Vanshika Singh¹; Brian Hicks¹; Bryan Lim¹; Sarah Graham¹; Soumya Nag¹; Peeyush Nandwana¹; Sudarsanam Babu¹; Brian Post¹; ¹Oak Ridge National Laboratory
    Feedstock costs and build rates are major roadblocks in addressing the supply chain constraints facing renewable energy castings with large-format metal additive manufacturing (AM). Compared to powders and welding wire, steelmaking feedstocks have significantly lower cost per unit mass but require refining to produce target alloys. Initial experiments were conducted to evaluate the refining abilities of the electroslag welding process with direct reduced iron (DRI) feedstocks and simulants in a molten slag bath and have demonstrated production of an iron phase of >98% purity. We compare furnace experiments with thermodynamic calculations and process kinetics to predict processing parameters at scale and conclude with a vision for further development of an in-situ refining electroslag additive manufacturing (RESAM) system for the high-throughput processing and alloying of low-cost steelmaking feedstocks.