Powder Materials Processing and Fundamental Understanding: Characterization and Analysis I
Sponsored by: TMS Materials Processing and Manufacturing Division, TMS: Powder Materials Committee
Program Organizers: Elisa Torresani, San Diego State University; Kathy Lu, University of Alabama Birmingham; Eugene Olevsky, San Diego State University; Ma Qian, Royal Melbourne Institute of Technology; Diletta Giuntini, Eindhoven University of Technology; Paul Prichard, Kennametal Inc.; Wenwu Xu, San Diego State University
Wednesday 2:00 PM
March 22, 2023
Room: 25B
Location: SDCC
Session Chair: Kathy Lu, Virginia Tech; Chu Lun Alex Leung, University College London
2:00 PM Invited
Reveal Laser-matter Interaction during Laser Powder Bed Fusion Using a Physical Twin, X-ray and Optical Imaging: Chu Lun Alex Leung1; Samy Hocine1; Andrew Farndell2; Rubén Lambert-Garcia1; Elena Ruckh1; Maureen Fitzpatrick1; Anna Getley1; Sebastian Marussi1; Marta Majkut3; Alexander Rack3; Nick Jones2; Peter Lee1; 1University College London; 2Renishaw plc.; 3European Synchrotron Radiation Facility
Laser powder bed fusion (LPBF) additive manufacturing is a digital manufacturing technology that makes 3D parts with complex geometry. LPBF can operate in continuous wave and modulated modes, however, the laser-matter interaction in these operation modes is complex and not well understood. To better understand the industrial LPBF process, we developed a next-generation physical twin using Renishaw’s RenAM500Q scan head coupled with X-ray and optical imaging. Here, we observe different types of vapor depression zones and defect generation mechanisms inside and above the laser-matter interaction under different laser powers, point exposure, jump delays, and beam diameter. Our preliminary results provide fundamental understanding of LPBF under industrial conditions, and hence crucial information for the development of the next-generation digital twin.
2:30 PM
Studying SiOC Atomic Structures via Synchrotron X-ray and Reactive Force Field Potential Studies: Kathy Lu1; Harrison Chaney1; 1Virginia Polytechnic Institute and State University
Silicon oxycarbide (SiOC) is a unique system that can generate various compositions and microstructures via different polymeric precursors and pyrolysis conditions. However, understanding of the resulting atomic structures, such as nanocluster phase types and sizes as well as atomic coordination, is lacking. In this study, new nanocluster phase identification and atomic pair distribution functions of different carbon-containing SiOC ceramics pyrolyzed at 1200°C and 1500°C were investigated. Also, a new ReaxFF molecular dynamics modeling approach was developed to understand the nanocluster size and distribution as well as atomic radial distribution function. The experimental and simulation data are compared to uncover the effects of starting polymer precursor compositions and pyrolysis temperatures on the evolution of atomic microstructures and nanosized phase regions of different SiOCs.
2:50 PM
Eu-doped Ca4-x-y(Sr,Ba)xEuyLaO(BO3)3 Compounds for Efficient White-light Illumination: Senam Tamakloe1; Mahdi Amachraa1; Jakoah Brgoch2; Shyue Ping Ong1; Olivia Graeve1; 1University of California San Diego; 2University of Houston
White light-emitting diodes produce high luminous brightness with low energy consumption. However, their low correlated color temperature and low color rendering index limit their white light quality caused by a deficiency in the red-light component. In this study, we report on the synthesis and photoluminescent properties of a red-emitting oxyborate phosphor Ca4-x-y(Sr,Ba)xEuyLaO(BO3)3 (M = Sr, Ba where x = 0, 0.5, … 4; y = 0.05) for solid-state white-lighting applications. The powders were made by solution combustion synthesis with subsequent calcination steps. For our work, the red-shifted emissions were detected in the orange-red regions (580 to 720 nm) using a fluorescence spectrophotometer. The Sr/Ba substitution at Ca sites in the Ca4Eu0.05LaO(BO3)3 lattice can enhance the photoluminescence response and quality of the phosphor by increasing internal quantum efficiency. In general, our results indicate that our oxyborate phosphor can help produce warmer white light and improve white-light technologies.
3:10 PM
Composition Control and Analysis of Sub-stoichiometric Titanium Hydride Powders: Daniel Bufford1; Hua Wang1; Stewart Youngblood1; 1Sandia National Laboratories
Hydrogen in structural titanium alloys leads to unwanted embrittlement, however, embrittling effects are beneficial during processing as they allow crushing of bulk titanium sponge into powder. It is thus of great importance to understand and control hydrogen absorption and desorption. Titanium hydrides with formula TiHx exist over a range of compositions with 0 < x ≤ 2. Despite frequently traversing the full composition range during hydride/dehydride processing of titanium sponge into powder, compositions in the intermediate range are less often produced intentionally and thus have seen less investigation. Here we create sub-stoichiometric titanium hydride powders with tightly controlled compositions in the range of 1.5 < x ≤ 2, and discuss efforts to develop hydrogen quantification methods to validate these composition targets. Also discussed are effects of processing on particle size, surface area, and metallurgical impurity content. These efforts demonstrate what precision can be obtained during processing of these powder materials.
3:30 PM Break
3:50 PM
Advanced Materials for Neutron Detection Applications: Design and Synthesis of Alkaline-earth Doped Hexaborides: Alan Hirales1; Victor Vasquez2; Olivia Graeve1; 1University of California San Diego; 2University of Nevada, Reno
We present a structural analysis of two metal hexaboride solid solutions, Cax-1MxB6 and Srx-1MxB6 (x = 0, 0.1, 0.3, 0.5), where M can be Li, Na, or K, as the experimental concentration, x, is increased. The powders were synthesized by solution combustion synthesis, acid-washed with HCl, and characterized by X-ray diffraction (XRD), inductively coupled plasma mass spectrometry (ICP-MS), selected-area electron diffraction (SAED) and transmission and scanning electron microscopies (TEM and SEM). XRD proves a high crystallinity of the prepared powders and SEM demonstrates cubic morphologies. For identification of the concentration of dopants, ICP-MS on the dissolved powders was performed, showing a concentration of 1 to 3 at.%. Both SAED and TEM studies show a monocrystalline growth of the cubes in the [100] direction, and a constant lattice parameter. Together, these studies will contribute to the understanding of hexaboride properties tailoring for neutron detection applications.
4:10 PM
Characterising the Vapour Plume and Preferential Vaporisation of Alloy Elements during Laser Powder Bed Fusion Additive Manufacturing: Anna Getley1; Samy Hocine1; Elena Ruckh1; Rubén Lambert-Garcia1; Sebastian Marussi1; Peter Lee1; Mike Towrie2; Chu Lun Alex Leung1; 1University College London; 2Central Laser Facility, STFC
Additive Manufacturing (AM) is regarded as the next revolution in the manufacturing sector. Laser Powder Bed Fusion (LPBF), a subset of AM, enables the design freedom to create progressively complex metal components; during the process, a bed of alloy powder is fused into solid via layer-wise melting with a high-power laser. A critical limitation influencing LPBF is preferential vaporisation; a phenomenon describing the unequal loss of alloy elements from the laser-matter interaction zone, due to differing physical properties. Preferential vaporisation has been sparingly observed in AM-printed parts through destructive techniques. This study presents the first demonstration of in situ synchrotron radiography and chemical characterisation techniques to analyse surface composition changes in a non-destructive fashion. We apply these experimental methods to link keyhole dimensions with surface chemistry, and further report a process map of preferential vaporisation across an AM track, as a function of LPBF parameters, over multiple industrial alloys.
4:30 PM
Powder Quality and Cold Spray Processability Changes with Environmental Exposure: Jack Grubbs1; Bryer Sousa1; Danielle Cote1; 1Worcester Polytechnic Institute
The success of powder-based additive manufacturing (AM) processes relies greatly upon feedstock powder quality, necessitating thorough pre-process characterization to understand powder properties and behavior and inform proper processing decisions. This is important when considering powder handling and storage prior to AM, during which detrimental flowability and moisture content changes may result from environmental exposure, potentially causing adverse downstream processing effects. This study aims to systematically investigate the property-processing-performance relationships of semi-spherical and ultra-spherical Al 2024 powders in cold spray (CS) in the context of environmental exposure. Accordingly, powder drying treatments were explored as a pre-CS step; powder property/behavior and CS processability changes were evaluated after controlled temperature/humidity exposure; and particle size-dependent moisture content changes were examined after exposure. From such findings, practical data-driven powder handling and CS processing guidelines were developed based upon powder characterization data to ensure consistently successful material processing
4:50 PM
Discrete Element Method Based Simulations of Metal Powder Pouring and Raking Processes in Additive Manufacturing: Michael Fazzino1; Ummay Habiba1; Rainer Hebert1; Serge Nakhmanson1; 1University of Connecticut
Discrete Element Method based approach implemented in the LIGGGHTS package was used to construct ‘digital twins’ of Ti 6-4 powder pouring and raking processes. Adjustable parameters of the pouring process digital twin were validated by an ASTM B213 standard Hall Flowmeter Funnel experiment, with experimental data for the particle size distribution used as input. Validation included comparing the general shape of the particle pile, such as its diameter, height, and slope angles to the experimental results. Localparticle size distributions were obtained for different areas within the pile (e.g., top vs. bottom area), indicating the dominance of larger particles at the top of the pile, akin to the Brazil nut effect. Validated material parameters were then utilized in construction of a digital twin of the particle pile raking process over a powder bed, with local porosity and particle size distribution after the raking evaluated and compared with the experimental results.
5:10 PM
Friction and Wear Performance of Spark Plasma Sintered Nanocrystalline Al-Mg Materials: Amanendra Kushwaha1; Manoranjan Misra1; Pradeep Menezes1; 1University of Nevada, Reno
In the present investigation, nanocrystalline (NC) materials, such as pure Al and Mg-doped Al were manufactured using cryo-milling followed by the spark plasma sintering process. The changes in crystallite size were determined using X-ray diffraction. Hardness measurements were performed using a Vickers micro-hardness tester. The friction and wear performance of NC materials were studied using a tribometer. Results showed that the crystallite size decreased with increasing cryo-milling time. The decrease in crystallite size increased the hardness of NC materials. The increase in hardness resulted in a decrease in the coefficient of friction and wear rate. The Mg-doped Al material showed superior hardness, friction, and wear performance compared to pure Al. The underlying mechanisms for the reduction in crystallite size and its effect on hardness, friction, and wear performance will be discussed.