Additive Manufacturing: Beyond the Beam II: Material Deposition for Sinter Densification
Sponsored by: TMS Materials Processing and Manufacturing Division, TMS: Powder Materials Committee, TMS: Additive Manufacturing Committee
Program Organizers: Paul Prichard, Kennametal Inc.; James Paramore, Texas A&M University; Peeyush Nandwana, Oak Ridge National Laboratory; Nihan Tuncer, Desktop Metal

Wednesday 2:00 PM
March 17, 2021
Room: RM 4
Location: TMS2021 Virtual

Session Chair: Nihan Tuncer, Desktop Metal

2:00 PM
Wall Thickness Effects on Dimensional Variation, Microstructure, and Mechanical Properties in Stainless Steel Samples Manufactured Using a Bound Metal Deposition (BMD) Sintering Process: Joy Forsmark¹; Emily Wolbeck¹; Ignacio Arretche¹; Eric Poczatek¹; Yun Bai¹; Hiroko Ohtani¹; Sushmit Chowdhury¹; ¹Ford Motor Company
    The Bound Metal Deposition (BMD) process extrudes a bound metal mixture to a green part and then finishes with a sintering cycle to produce the final component. The process involves several steps and results in a final component that is approximately 15-20% smaller than the original green part. This process represents a way to prototype metal parts using Additive Manufacturing without the need for special environmental controls required for powder-based processes. However, the multiple processes involved (printing, debinding, and sintering) can result in dimensional variability in different directions in the part. This study measured the effects of wall thickness on the dimensions, microstructure, and hardness at different stages of the process and in different orientations to develop design rules and gain an understanding of the dimensional sintering scaling factors required to produce parts to match the input design CAD.

2:20 PM
Bi-metal Composite Material for Plastic Injection Molding Tooling Applications via Fused Filament Fabrication Process : Maxim Seleznev¹; Joe Roy-Mayhew¹; ¹Markforged Inc.
    Fused filament fabrication (FFF) technology, an additive manufacturing process traditionally used for building plastic objects, has been commercialized for making metal parts. Metal FFF uses metal powder filled plastic filaments, coupled with debinding and sintering operations, and can produce molds for plastic injection molding machines. Such molds would greatly benefit from the introduction of conformal cooling channels as well as an enhanced thermal conductivity of material they are made of, traditionally steel. Presented research is focused on development of such a material – a bi-metal composite of steel and copper - that was shaped into a mold with conformal cooling channels via application of the metal FFF process. The bi-metal composite exhibited thermal conductivity of 108 W/mK and 110 GPa modulus of elasticity in an as-manufactured condition. Results for processing, microstructure and thermal and mechanical properties of the new bi-metal composite material will be discussed in the presentation.

2:40 PM
Direct Ink Writing of Ceramic Architected Materials: Raphael Thiraux¹; Lorenzo Valdevit¹; ¹University of California, Irvine
    Technical ceramics have exceptional high-temperature mechanical properties, but unfortunately their high crack sensitivity and high melting point make it challenging to manufacture complex shapes ceramic structures with sufficient toughness. Additive manufacturing techniques could potentially overcome this challenge, enabling fabrication of large-scale complex-shape artifacts with architected internal topologies characterized by microscale geometrical features with controlled defect population. Direct ink writing, i.e. the three-dimensional extrusion of a rheologically complex fluid, is a particularly versatile technique, thanks to its almost unlimited materials palette. Here, we fabricate micro-architected ceramic structures using direct ink writing (DIW) of an alumina nanoparticle-loaded ink, followed by sintering. First, we characterize the rheology of the ink and extract optimal printing parameters. Next, we investigate the effects of the printing and sintering parameters on the mechanical properties of the ceramic material. Finally, we extend this investigation to the design, fabrication, and characterization of strong 2D and 3D ceramic architected materials.

3:00 PM
Beyond the Beam Additive Manufacturing of Titanium Alloys: James Paramore¹; Brady Butler¹; Matthew Dunstan¹; Daniel Lewis¹; Michael Hurst¹; Laura Moody¹; ¹U.S. Army Research Laboratory
    Due to their unique combination of properties, titanium alloys can be regarded as a “one size fits all” solution for many metal additive manufacturing (AM) applications. Such a solution could significantly simplify or eliminate material selection and/or feedstock inventorying. However, titanium alloys are also particularly susceptible to thermal processing, meaning the complex thermal histories of beam-based AM (e.g. powder bed fusion and directed energy deposition) can produce unacceptable and/or unpredictable results. Non-beam metal AM technologies (e.g. material extrusion AM and binder jetting) hold significant promise, as they enable more predictable microstructural and mechanical property engineering. However, these technologies have their own hurdles, as they often require binders that may contaminate titanium alloys and/or require significant densification during subsequent sintering processes. This talk will discuss the various benefits and hurdles of non-beam AM of titanium alloys through the lens of both theory and published literature, as well as original experimental results.

3:20 PM
Spatial Architecture of Copper Fillers in Additively Manufactured PLA-matrix Composite: Nazmul Haque¹; Hadi Noori¹; ¹Oklahoma State University
    The fused deposition modeling (FDM) process was utilized as a platform to customize the spatial architecture of copper fillers in the 3-D structure of the PLA matrix. Prior to the extrusion process in FDM, the surface of the PLA filament was knurled to make grooves, which were selectively filled with copper powders. Monolayer samples were manufactured with a layer height of 0.6 mm, and a width of 25 mm. The PMC was devised to have a 20 mm length at the middle of samples with 90 mm length. The samples were subjected to uniaxial tensile tests to assess their fracture energy. For all samples, the fracture was brittle at the interface between the layers. The samples with PMC sections showed inferior fracture strength in comparison with pure PLA samples. This result was attributed to the formation of voids at the interface between copper powders and the PLA matrix.