A5002110697- Additive Manufacturing Materials and Processes
- Rare-earth and actinide compounds
- Welding Techniques and Residual Stresses
- Iron-based superconductors research
- Additive Manufacturing and 3D Printing Technologies
- Inorganic Chemistry and Materials
- Laser Material Processing Techniques
- Thermography and Photoacoustic Techniques
- High Entropy Alloys Studies
- Crystallization and Solubility Studies
- X-ray Diffraction in Crystallography
- Thermal Expansion and Ionic Conductivity
- Advanced X-ray and CT Imaging
- Advanced Thermoelectric Materials and Devices
- Laser-induced spectroscopy and plasma
- Topological Materials and Phenomena
- Magnetic and transport properties of perovskites and related materials
- Industrial Vision Systems and Defect Detection
- Ocular and Laser Science Research
- Graphene research and applications
- Semiconductor Lasers and Optical Devices
- Thermal properties of materials
- Titanium Alloys Microstructure and Properties
- Magnetic Properties of Alloys
- Thermodynamic and Structural Properties of Metals and Alloys
Lawrence Livermore National Laboratory
2016-2024
Northwestern University
2013-2017
Northwest University
2013-2016
Abstract Laser powder bed fusion additive manufacturing is an emerging 3D printing technique for the fabrication of advanced metal components. Widespread adoption it and similar technologies hampered by poor understanding laser-metal interactions under such extreme thermal regimes. Here, we elucidate mechanism pore formation liquid-solid interface dynamics during typical laser conditions using in situ X-ray imaging multi-physics simulations. Pores are revealed to form changes scan velocity...
Circumventing spatter Laser powder bed fusion is an additive manufacturing technique that laser-melts layer by to build a three-dimensional (3D) part. Khairallah et al. used experiments and multiphysics model determine the origin of melt defect formation degrade properties built parts (see Perspective Polonsky Pollock). Informed modulation laser power important avoid disturbing creating shadowing. This reduces pore formations leads more uniform 3D-printed parts. Science , this issue p. 660 ;...
Layer-to-layer height measurements of additively manufactured 316L stainless steel using high speed spectral-domain optical coherence tomography (SD-OCT) are presented. Layers built up an open architecture laser powder bed fusion machine while made in-line along the process path following each layer print. Printed cubes, with and without internal ‘overhang’ channel, were to investigate effect scanning parameters on surface structure. scan rotation strategy significantly impacts roughness...
Advanced in situ characterization is essential for determining the underlying dynamics of laser-material interactions central to both laser welding and rapidly expanding field additive manufacturing. Traditional techniques leave a critical experimental gap understanding complex subsurface fluid flow metal evaporation inherent laser-induced heating metal. Herein, ultra-high-speed transmission X-ray imaging revealed be bridging this information gap, particularly via comparison with validation...
Abstract Thermoelectric (TE) materials convert heat energy directly into electricity, and introducing new with high conversion efficiency is a great challenge because of the rare combination interdependent electrical thermal transport properties required to be present in single material. The TE defined by figure merit ZT =( S 2 σ ) T / κ , where Seebeck coefficient, conductivity, total absolute temperature. A p‐type thermoelectric material, CsAg 5 Te 3 presented that exhibits ultralow...
In situ X-ray-based measurements of the laser powder bed fusion (LPBF) additive manufacturing process produce unique data for model validation and improved understanding. Synchrotron X-ray imaging diffraction provide high resolution, bulk sensitive information with sufficient sampling rates to probe melt pool dynamics as well phase microstructure evolution. Here, we describe a laboratory-scale LPBF test designed accommodate experiments at synchrotron source during operation. We also present...
Abstract Laser powder bed fusion (LPBF) is a method of additive manufacturing characterized by the rapid scanning high powered laser over thin metallic to create single layer, which may then be built upon form larger structures. Much melting, resolidification, and subsequent cooling take place at much higher rates with thermal gradients than in traditional metallurgical processes, this occurring below surface. We have used situ speed X-ray diffraction extract subsurface following...
In-situ process monitoring of additively manufactured parts has become a topic increasing interest to the manufacturing community. In this work, acoustic measurements recorded during laser powder-bed fusion (L-PBF) were used detect onset keyhole pores induced by lasing process. Post-build radiography was identify locations in build. The pore spatially and temporally registered with time-series position pressure specific partitions signals which correspond formation. Ensemble empirical mode...
Laser powder bed fusion (LPBF) metal additive manufacturing provides distinct advantages for aerospace and biomedical applications. However, widespread industrial adoption is limited by a lack of confidence in part properties driven an incomplete understanding how unique process parameters relate to defect formation ultimately mechanical properties. To address that gap, high‐speed X‐ray imaging used probe subsurface melt pool dynamics void‐formation mechanisms inaccessible other monitoring...
Laser powder bed fusion (LPBF) additive manufacturing and laser welding are powerful metal processing techniques with broad applications in advanced sectors such as the biomedical aerospace industries. One common process variable that can tune laser-material interaction dynamics these two is adjustment of composition pressure atmosphere which conducted. While some physical mechanisms governed by ambient well known from literature, it remains unclear how extend to distinct conditions LPBF. In...
Metal parts produced by laser powder bed fusion (LPBF) additive manufacturing exhibit characteristic microstructures comparable to those observed in welding. The primary cause of this microstructure is rapid, localized heating and cooling cycles, which result extreme thermal gradients where material solidification followed fast the solid state. final mechanical performance are also influenced pore formation caused melt pool fluid dynamics. Here, we use high speed, situ X-ray diffraction...
Abstract We present our recent development of an integrated mesoscale digital twin (DT) framework for relating processing conditions, microstructures, and mechanical responses additively manufactured (AM) metals. In particular, focusing on the laser powder bed fusion technique, we describe how individual modeling simulation capabilities are coupled to investigate control AM microstructural features at multiple length time scales. review prior case studies that demonstrate schemes, in which...
A new polymorph of the RE2Ru3Ge5 (RE = Pr, Sm, Dy) compounds has been grown as single crystals via an indium flux. These crystallize in tetragonal space group P4/mnc with Sc2Fe3Si5-type structure, having lattice parameters a 11.020(2) Å and c 5.853(1) for RE 10.982(2) 5.777(1) 10.927(2) 5.697(1) Dy. materials exhibit structural transition at low temperature, which is attributed to apparent charge density wave (CDW). Both high-temperature average crystal structure low-temperature...
Abstract Thermoelectric (TE) materials convert heat energy directly into electricity, and introducing new with high conversion efficiency is a great challenge because of the rare combination interdependent electrical thermal transport properties required to be present in single material. The TE defined by figure merit ZT =( S 2 σ ) T / κ , where Seebeck coefficient, conductivity, total absolute temperature. A p‐type thermoelectric material, CsAg 5 Te 3 presented that exhibits ultralow...
The rendering in the background shows a metal component being manufactured through laser powder bed fusion additive manufacturing. film strip contains frames from high-speed X-ray imaging revealing previously unseen void defect formation during build which furthers understanding of material properties and performance these components. Further details can be found article number 1900455 by Johanna Nelson Weker co-workers.
Laser powder bed fusion (LPBF) is a highly dynamic multi-physics process used for the additive manufacturing (AM) of metal components. Improving understanding and validating predictive computational models require high-fidelity diagnostics capable capturing data in challenging environments. Synchrotron x-ray techniques play vital role validation as they are only situ diagnostic imaging sub-surface melt pool dynamics microstructure evolution during LPBF-AM. In this article, laboratory scale...
Various nondestructive diagnostic techniques have been proposed for in situ process monitoring of laser powder bed fusion (LPBF), including melt pool pyrometry, whole-layer optical imaging, acoustic emission, atomic emission spectroscopy, high speed and thermionic emission. Correlations between these signals defect formation demonstrated with having shown to predict pore especially confidence recent machine learning studies. In this work, time-resolved data are collected both the conduction...
Accurate noncontact surface-temperature measurements during laser-based materials processing remain challenging due to the difficulty of establishing reliable emissivity values as a function temperature and wavelength. Direct measurement is difficult, may be changing constantly in laser-material interaction region, where gradients are extreme surface displacement can complicate measurement. Here, we present hyperspectral imaging method using multiwavelength camera capture spectral radiance...