2023 Annual International Solid Freeform Fabrication Symposium (SFF Symp 2023): Materials: Metals-Characterization of AM Processes and Materials
Program Organizers: Joseph Beaman, University of Texas at Austin
Tuesday 1:40 PM
August 15, 2023
Room: 602
Location: Hilton Austin
Session Chair: Halsey Ostergaard, University of Sydney
1:40 PM
In- and Ex-situ Neutron Characterization of Metal Additive Processes and Microstructures: Halsey Ostergaard1; Jitendra Mata2; Elliot Gilbert2; Julie Cairney1; Anna Paradowska1; 1The University of Sydney; 2Australian Nuclear Science and Technology Organisation
Two novel neutron techniques in AM are demonstrated: ultra-small and small-angle neutron scattering (U/SANS) for micron and submicron precipitate analysis and in-situ diffraction during laser metal deposition (LMD). With extension into the USANS range, SANS is sensitive to precipitate structures below a few microns and provides volume-averaged data that complement other techniques. U/SANS, APT, and TEM were used to study LPBF Ni superalloy 718 and assess distribution, shape, and texture of both nano-scale intracellular strengthening precipitates as well as micron-scale intercellular delta phase precipitation. First results in 316L stainless from a new in-situ neutron system for LMD are summarized. Designed for use on multiple beamlines, the system is capable of in-situ sub-surface process monitoring in either diffraction or imaging modes. Diffraction results are correlated against ex-situ residual stress, microstructural, and hardness analyses.
2:00 PM
X-Ray Computed Tomography: A Game-Changer for Parameter Control in Additive Manufacturing: Curtis Frederick1; 1Carl Zeiss Microscopy
Quality control of AM parts is still a major challenge due to the complex geometries, rough surfaces, and asymmetric deformation of as printed parts. X-ray computed tomography (CT) is a non-destructive technique that can provide valuable insights into the internal structure and properties of AM parts. In this presentation, we will discuss the benefits of using X-ray CT in researching AM, including the ability to detect defects such as cracks, voids, and inclusions, and to measure the density and deformation of the AM part. We will also highlight the advantages of using advanced CT techniques, such as high-resolution imaging and reconstruction enhanced by deep learning models, to gain a better understanding of the microstructure and mechanical behavior of AM parts. This presentation will share the insights gained from using X-ray CT to optimize the AM process, improve part quality, and reduce costs in various industries and applications of AM.
2:20 PM Cancelled
In situ Layer-wise Optical Imaging for Defect Detection during Laser Powder Bed Fusion: Sanam Gorgannejad1; Wanda Wang1; Gabe Guss1; Steven Hoover1; Justin Patridge1; Nicholas Calta1; 1Lawrence Livermore National Laboratory
Ensuring high-quality parts and process repeatability through systematic fault detection and control is a well-established goal in the laser powder bed fusion (LPBF). In situ process monitoring approaches are increasingly favored for real-time quality assurance. Despite the extensive research aimed at developing novel monitoring modalities, it is imperative to leverage the already established techniques to their fullest potential that allows for fast adaptation in manufacturing settings. Optical cameras are widely integrated into commercial LPBF machines, providing images of the powder bed subsequent to powder spread and fusion at every layer. In this study, we have adopted and developed methodologies to exploit the layer-wise images to detect printing defects and three-dimensional reconstruction of the components to facilitate part qualification prior to conducting XCT.Prepared by LLNL under Contract DE-AC52-07NA27344.
2:40 PM Cancelled
Challenges and Opportunities in Acoustic Emission Monitoring for Quality Control of Directed Energy Deposition Additive Manufacturing: Ehsan Dehghan Niri1; Anusuya Vellingiri2; Steven Hespeler3; Andi Wang1; 1Arizona State University; 2New Mexico State University ; 3New Mexico State University
Acoustic Emission (AE) is a proven nondestructive testing (NDT) method that has demonstrated effectiveness in monitoring infrastructures, testing pressure vessels, and qualifying manufactured components during and after manufacturing processes. Ultrasound stress waves captured during AE monitoring, has been found to contain useful information regarding potential incidents resulting from normal or abnormal events during manufacturing processes. Despite its maturity in monitoring infrastructures, AE encounters several challenges when applied to monitoring additive processes such as directed energy deposition (DED). This article presents a summary of the challenges and opportunities associated with using AE in this context, using several examples to illustrate key points. In particular, the article highlights the strong statistical correlation between the high frequency AE signals and the AM process parameters, as well as the quality of the metallic parts produced.
3:00 PM
Absorptivity Behavior of High Reflectivity Aluminum and Copper Alloys During Laser Powder Bed Fusion: Sagar Patel1; Troy Allen2; David Deisenroth3; Madison Reed2; Peyman Alimehr1; Sergey Mekhontsev3; James Fraser2; Mihaela Vlasea1; 1University of Waterloo; 2Queen's University; 3National Institute of Standards and Technology
The higher reflectivity and conductivity of aluminium and copper alloys, when compared to other commonly used alloys, pose unique challenges when being manufactured using laser powder bed fusion (LPBF). As such, the physics of laser-material interactions are complex for LPBF of aluminium and copper alloys, leading to a costly process parameter development cycle. In this work, in situ reflectivity measurements are carried out for one aluminium and one copper alloy and compared to melt pool depths for multiple process parameters spanning the conduction, transition, and keyhole melting modes. The measurements for aluminium are carried out using an integrating sphere setup on a commercial LPBF system; while for copper, an integrating hemisphere on the LPBF testbed at NIST is used. The inferred absorptivity values are then analyzed using dimensionless parameters to develop material class specific absorptivity scaling laws, that would accelerate the process parameter development cycle for aluminium and copper alloys.
3:20 PM
Machinability of Additively Made Alloys: A Case Study of Ti64 and A205 Alloys: Otto Randolph1; Aamer Kazi1; Bruce Tai1; Ryan Zvanut2; 1Texas A&M University; 2Kansas City National Security Campus
It is widely known that additively manufactured (AM) metal parts require post-processing to achieve dimensional tolerances comparable to those of cast or wrought metals. One common post-processing technique is machining, but AM alloys can respond differently to machining due to their unique microstructures formed in the thermal cycle. This research attempts to characterize the machinability of two alloys in turning, Ti64 and A205 aluminum, using conventionally made rods as a baseline to compare to AM equivalents. The main variables are feed and speed. In each cutting test, vibrational response, specific cutting energy, surface roughness, and images of the chips and cut surface are recorded to assess the machinability. The results show noticeable differences between AM and baseline parts in vibration and surface finish. These differences are correlated to and can be explained by the differences in their microstructures. Machining recommendations are provided at the end of this study.
3:40 PM
Additively Manufactured Lunar Rover Wheel Case Study: Richard Hagen1; Brian Gibson2; 1NASA JSC; 2Oak Ridge National Laboratory
The current state of the art to manufacture Lunar Wheels can be expensive and time consuming. In an effort to reduce time and cost, Oak Ridge National Laboratory uses a large format metal additive system to produce a wheel for the Johnson Space Center to evaluate. The purpose of this case study is to compare the current VIPER wheel to an additively manufactured wheel design optimized for printing. The presentation will highlight the design differences between the current VIPER wheel and the potential improvements made possible with AM. Additionally, there will be a discussion about the metal AM process used for fabricating a large part and how well the as built part corresponds to the model. Finally, results of a performance comparison of the VIPER wheel to the printed wheel will be presented to show if there is an advantage with the new design features not currently possible.