2024 Annual International Solid Freeform Fabrication Symposium (SFF Symp 2024): Materials: Metals V
Program Organizers: Joseph Beaman, University of Texas at Austin
Wednesday 8:00 AM
August 14, 2024
Room: 602
Location: Hilton Austin
Session Chair: Yash Parikh, EOS of North America, Inc.
8:00 AM
Study of Using a Secondary Pulsed Laser for Process Control in Laser Powder Bed Fusion: Dongping Terrel-Perez1; CE Kim1; Gabe Guss1; Thejaswi Tumkur Umanath1; 1Lawrence Livermore National Laboratory
Laser processing enables metal printing with 3D intricate geometries and high throughput. In laser powder bed fusion (L-PBF), high laser intensities and scan speeds lead to high solidification growth rates and induce large thermal gradients in and near the melt pool, leading to coarse, textured microstructure. Heat and mass transport mechanisms are strongly dictated by melt-pool behaviors. Here, we implement an ultrashort pulsed laser as a secondary beam, in combination with a primary cw laser beam. We track the chevron patterns formed on a laser weld track (in SS316L) upon solidification, and correlate extracted cooling rates to the surface roughness of printed tracks. We observe that unique optical properties of such dual-beam, temporal modulation approach results in control over cooling rates, surface quality and microstructure. The unique combination of cw and ultrashort pulsed lasers will provide additional degrees of freedom for improving microstructural and mechanical properties in L-PBF.
8:20 AM
Improving the Design for Additive Manufacturing Process with Design of Experiments to Characterize Geometry-Dependent Porosity and Surface Roughness: Federico Venturi1; Robert Taylor1; 1University of Texas Arlington
The characterization of defects in additive manufacturing (AM) is key in determining the performance indicators used for validation of a material or component. However, due to the thermal nature of AM, traditional methods of validation may fail to capture geometric effects on the resulting thermal history of a build. Thus, a new methodology of validation must be considered to build on the effect of not only the feedstock material, but also the final geometry intended for use. Through the use of computed tomography scanning, porosity and surface roughness of AlSi10Mg specimens, designed to incorporate various geometric features, are analyzed. These features, such as fillet radii, thickness, and overhang angle, are then tied to their defect characteristics to create a model of the effect of geometry. Subsequent optimization of these modeled correlations is employed in finite element modeling using Altair Optistruct to maximize the performance of the final component geometry.
8:40 AM
Blue Laser Powder-blown Directed Energy Deposition of Niobium: Rujing Zha1; Jihoon Jeong2; Nhung Nguyen1; KenHee Ryou1; Faith Rolark1; James Male3; Jian Cao1; 1Northwestern University; 2Texas A&M University; 3QuesTek Innovations, LLC
The push towards ever higher operating temperatures in gas turbine engines has led engine hot section development to explore the use of refractory metals such as niobium in place of traditional superalloys. Laser powder directed energy deposition (DED) enables grading niobium alloy variants, increasing design freedom. However, niobium alloys’ high melting temperature and low absorptivity to near infrared laser light complicate fabrication of niobium alloys via laser DED. In this work, we address this challenge by developing laser powder DED of pure niobium using a 500 W 450 nm wavelength blue laser. Single trace experiments were performed to correlate laser power and powder flow rate with dilution and clad height. Using the optimal process settings, an over 99% densified cube was fabricated. Additional cube builds correlated scan speed and laser power with densification and grain size. This work paves the way for flexible future fabrication of niobium alloy engine components.
9:00 AM Cancelled
Prediction of the Spreadability of Metal Powders: The Last Developements: Aurelien Neveu1; Filip Francqui1; 1GranuTools
The spreadability of powders,i.e. their ability to produce smooth and homogeneous layers, is an essential property to guarantee the good quality of the parts produced in powder-bed based AM processes. However, evaluating the spreadability of materials during production is usually not feasible due to the cost associated with the minimum batch volume to fill in the machine and the time required to empty and clean the machine between each test. The Cohesive Index metric (GranuDrum, Granutools, Belgium) has been demonstrated to be well correlated with the homogeneity of the deposited layers in an SLM printer (ISO/ASTM TR 52952:2023). This indicates the strong relationship between powder cohesiveness and spreadability. These results opened up new perspectives to predict the spreadability of materials at the formulation stage, without having to produce large batches. Also, suppressing the need to fill the machine is nice to have to reduce the material cost and machine time.
9:20 AM
In-Situ Ultra-Fast Laser Processing in LPBF for Surface Quality Improvement and Defect Removal: Gonzalo Reyes-Donoso1; Justin Krantz1; Cody Lough2; Ben Brown2; Robert Landers1; Edward Kinzel1; 1University of Notre Dame; 2Kansas City National Security Campus
Laser Powder Bed Fusion (LPBF) provides the flexibility to fabricate complex components; however, the manufactured parts often require substantial post-processing, which is limited for internal surfaces and complex shapes. Experimental studies are conducted on an LPBF system containing a fiber laser for processing and a femtosecond laser for in-situ spectroscopy and ablation. Process maps for laser ablation and polishing of stainless-steel 3D printed surfaces are generated. Experimental studies are conducted to determine part contour improvements using layer-by-layer contour ablation and contour surface effects of using the femtosecond laser for powder processing. We explore using the femtosecond laser for layer defect repair by removing material pockets via ablation. The Department of Energy’s Kansas City National Security Campus funded this work. *The Department of Energy’s Kansas City National Security Campus is operated and managed by Honeywell Federal Manufacturing & Technologies, LLC under contract number DE-NA0002839.NSC-614-6141 04/2024 Unclassified Unlimited Release
9:40 AM
Location-Specific Engineered Microstructure Using Interpenetrating Lattices in Laser Powder-Bed Fusion: Bharath Bhushan Ravichander1; Shweta Hanmant Jagdale1; Golden Kumar1; 1University of Texas at Dallas
Laser powder-bed fusion (LPBF) is a prominent additive manufacturing process known for its precision in fabricating intricate metal components. The nature of the LPBF process enables the fabrication of parts with location-specific microstructures. However, due to the process's rapid heating and cooling cycles, the microstructure of the fabricated parts is predominantly anisotropic. To address this challenge, this study introduces interpenetrating lattice-based laser rescanning to control the local solidification conditions during the LPBF process and modify the location-specific microstructure in IN718 samples. The interpenetrating lattice-based laser rescanning approach significantly influenced the melt pool dimensions, grain size distribution, and microhardness. The results demonstrate the formation of a controlled combination of equiaxed and columnar microstructure. The study showcases the potential of interpenetrating lattice-based laser rescanning as a promising avenue for achieving precise control over the microstructure in LPBF, opening new avenues to enhance the performance and functionality of additively manufactured metal components.
10:00 AM
Multi-Material Integration in Laser Powder Bed Fusion: Bharath Bhushan Ravichander1; Golden Kumar1; 1University of Texas at Dallas
The laser powder bed fusion (LPBF) process can produce net-shaped intricate metal components, but typically, the LPBF machines are designed for handling a single metal powder. This study evaluates the integration of an additional powder dispensing and removal system to enable the fabrication of multi-material metal components using a commercial LPBF printer. The system allows the simultaneous dispensing of two or potentially more metal powders during the recoating process, opening new opportunities for functional grading in LPBF metal parts. A crack-free SS316L-IN718 bimetallic specimen was fabricated to demonstrate the capability of the modified LPBF system. Optical and scanning electron microscopy were used to characterize the interface's melt pool geometry and composition. The results show that a simple and detachable powder dispensing system can incorporate dissimilar metals in LPBF parts.
10:20 AM Break
10:40 AM
GAN-Based High-Throughput Single Track Characterization to Reduce Variability and Experimental Costs in Laser Powder Bed Fusion: Jiahui Ye1; John Coleman2; Gerald Knapp2; Amra Peles2; Chase Joslin2; Alex Plotkowski2; Alaa Elwany1; 1Texas A&M University; 2Oak Ridge National Laboratory
Most process optimization methods in laser powder bed fusion additive manufacturing rely on single-track experiments, an efficient screening step to conduct preliminary exploration of large processing parameter space and guide subsequent manufacturing of coupon, mechanical test samples, and ultimately full-scale parts. However, most approaches overlook variability in single-track experiments due to melt pool instabilities. Replicates are thus needed to account for these variabilities. We propose a new high-throughput single-track analysis method based on Generative Adversarial Network (GAN) for the rapid investigation of heteroscedastic variance in tracks while minimizing labor-intensive efforts. Next, we couple this method with physics-based defect criteria to develop optimal process maps with uncertainty bands. We further show how this approach is readily generalizable to different processing conditions with minimal computational and experimental burden. This research was sponsored by NSF, the U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy, Advanced Materials and Manufacturing Technology Office.
11:00 AM
Process Parameter Effects on the Mechanical Behavior and Microstructure of Fused Filament Fabricated 17-4 PH: Sina Alipour1; Le Zhou1; Allison Murray1; 1Marquette University
Fused filament fabrication (FFF), as an appealing alternative to conventional manufacturing techniques, provides several competitive advantages, including reduced production costs, design freedom for complicated geometries, and ease of use. However for metal FFF using metal-filled filaments, there are gaps in our understanding of the printing and post-processing parameters, which limit the ability to control the material properties. Using a low-cost FFF printer and BASF 17-4 PH stainless steel filament as a foundation, this study explores the debinding and sintering conditions, and examines the impact of FFF processing parameters on the structural and mechanical integrity of the printed parts. The effects of printing orientation, extrusion temperature, print speed, infill patterns, and post-processing conditions on density, microstructure and mechanical properties were explored. An in-house debinding and sintering method was developed and investigated. Initial findings indicate promise for FFF in producing metal components, but the results are highly dependent on processing parameters.
11:20 AM
Fabrication of Zr-Based Bulk Metallic Glass from Crystalline Foil Using Laser Foil Printing Process: Chia-Hung Hung1; Yu-Xiang Wang1; 1National Cheng Kung University
In this study, the crystalline zirconium-based (Zr-based) alloys foil was used to fabricate bulk metallic glass using the laser-foil-printing (LFP) process. Through laser spot pattern welding, the crystalline phase of NiZr2 and its oxides in Zr-based crystalline foil were remelted and disordered to form bulk metallic glass (BMG) parts. BMG parts fabricated from amorphous foil and crystalline foil were characterized and compared for the amorphous structure through X-Ray diffraction (XRD). The microhardness revealed similar mechanical properties of LFP-fabricated BMGs using different crystalline types of feedstocks. Moreover, in the transmission electron microscope (TEM) results of BMGs, the select area electron diffraction (SAED) pattern and the bright-field (BF) images show a typical amorphous structure, indicating the feasibility of using the crystalline foil.
11:40 AM
High Strength Magnesium Alloy Parts Fabricated by Laser-Foil-Printing Process: Chia-Hung Hung1; Zhen-Jie Zhao1; Tunay Turk2; Sung-Heng Wu2; 1National Cheng Kung University; 2Missouri University of Science and Technology
In this study, the laser-foil-printing (LFP) process has been successfully used to fabricate the AZ31B magnesium (Mg) alloy with high strength and ductility in a risk-free way. Compared to the laser powder bed fusion (L-PBF) processes, the LFP process enhances resistance to oxidation and mitigates the potential explosive risks associated with Mg by using foil as the feedstock material. The microstructure, hardness, and tensile properties of the LFP-fabricated AZ31B parts (approximately 99.9% relative density) were characterized. The tensile results indicated that the ultimate tensile strength (UTS) and elongation (EL) exhibit similarity and isotropy along the laser scanning and building directions, in which possesses superior mechanical properties than other laser additive manufacturing (LAM) processes. Through electron backscatter diffraction (EBSD) technique, the grain size of LFP parts was finer compared to LAM-fabricted parts, due to its higher cooling rate.
12:00 PM
Upcycling Machining Chips for Additive Friction Stir Deposition Feedstock Production: Sweta Baruah1; Tony Spezia1; Rob Patterson1; Jose Nazario1; Tony Schmitz1; 1University of Tennessee Knoxville
Additive friction stir deposition (AFSD) is a novel and environment-friendly additive manufacturing (AM) process that uses a rotating tool to generate frictional heat and plastic deformation, allowing metals to be deposited layer by layer onto a substrate. This solid-state process eliminates melting and solidification and provides an avenue for upcycling machined metallic chips to produce feedstock rods. This paper presents a chip compactor design integrated into a hydraulic press using a die set and ram carriage. Through the application of controlled compressive mechanical forces under both cold and warm working conditions, the system enables aluminum (Al6061) rods to be produced from machining chips with 86% relative density with respect to wrought Al6061. The chip compactor design is described and its implications for AFSD sustainability within a circular economy model is examined.
12:20 PM
Microstructural and Mechanical Heterogeneity Observed in Additive Friction Stir Deposition Ti-6Al-4V: Eric Heikkenen1; Rob Patterson1; Joshua Kincaid1; Peter Metz1; Suresh Babu1; Tony Schmitz1; 1University of Tennessee
Additive friction stir deposition (AFSD) was used to deposit Ti-6Al-4V both above and below the beta transus temperature. The stir zone region microstructures varied from equiaxed alpha to bimodal to lamellar in the stir zone. Below the final stirred regions, micrographs revealed microstructural heterogeneity in the form of etching bands, while hardness maps correlated the observed differences to mechanical heterogeneity. This heterogeneity was seen to vary periodically both on a single layer-scale as well as a longer-range, multi-layer scale. These variations correspond to process stoppages related to material reload events inherent to a discrete feed system. These findings suggest that thermal gradients should be a consideration for AFSD of titanium, even with a continuous feed system.