A5003287995- Additive Manufacturing Materials and Processes
- Additive Manufacturing and 3D Printing Technologies
- Laser Material Processing Techniques
- Welding Techniques and Residual Stresses
- Laser-induced spectroscopy and plasma
- Quantum, superfluid, helium dynamics
- High Entropy Alloys Studies
- Manufacturing Process and Optimization
- Surface Roughness and Optical Measurements
- Advanced Chemical Physics Studies
- High-pressure geophysics and materials
- Spacecraft and Cryogenic Technologies
- Atomic and Subatomic Physics Research
- Atomic and Molecular Physics
- Gastric Cancer Management and Outcomes
- Plasma Diagnostics and Applications
- Computational Fluid Dynamics and Aerodynamics
- Advanced Surface Polishing Techniques
- Nuclear reactor physics and engineering
- Superconducting Materials and Applications
- Luminescence Properties of Advanced Materials
- Engineering Technology and Methodologies
- Inorganic Fluorides and Related Compounds
- Advanced machining processes and optimization
- Thermography and Photoacoustic Techniques
Lawrence Livermore National Laboratory
2016-2025
Los Alamos National Laboratory
2017
Planetary Science Institute
2008
University of California, Berkeley
2008
University of Illinois Urbana-Champaign
2005-2007
The production of metal parts via laser powder bed fusion additive manufacturing is growing exponentially. However, the transition this technology from prototypes to critical hindered by a lack confidence in quality part. Confidence can be established fundamental understanding physics process. It generally accepted that will increasingly achieved through modeling and simulation. there are significant physics, computational, materials challenges stemming broad range length time scales...
Understanding laser interaction with metal powder beds is critical in predicting optimum processing regimes bed fusion additive manufacturing of metals. In this work, we study the denudation powders that observed near scan path as a function parameters and ambient gas pressure. We show depletion particles zone immediately surrounding solidified track due to competition between outward vapor flux directed away from spot entrainment shear flow driven by jet at melt track. Between atmospheric...
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...
The results of detailed experiments and finite element modeling metal micro-droplet motion associated with additive manufacturing (AM) processes are presented. Ultra high speed imaging melt pool dynamics reveals that the dominant mechanism leading to ejection in a laser powder bed fusion AM is not from induced recoil pressure as widely believed found welding processes, but rather vapor driven entrainment micro-particles by an ambient gas flow. physics droplet under strong evaporative flow...
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 ;...
We have calculated the absorption of laser light by a powder metal spheres, typical employed in powder-bed fusion additive manufacturing. Using ray-trace simulations, we show that is significantly larger than its value for normal incidence on flat surface, due to multiple scattering. investigate dependence content (material, size distribution, and geometry) beam size.
The metal laser powder bed fusion additive manufacturing process uses high power lasers to build parts layer upon by melting fine powders. Qualification of produced using this technology is broadly recognised as a significant challenge. Physics based models have been identified being foundational qualification additively manufactured parts. In the present article, multiscale modelling strategy described that will serve foundation which control and part can be built. This includes model at...
Additive manufacturing (AM) promises to revolutionize by producing complex parts with tailored mechanical properties through local microstructure control. The main challenge is control or prevent columnar (elongated) growth morphology which prevalent in AM parts. Here, we elucidate mechanisms of that promote favorable equiaxed grains (aspect ratio close 1) using a laser beam shaping strategy. This requires an accurate thermal profile only captured advanced predictive simulation couples full...
Additively manufactured (AM) metals are often highly textured, containing large columnar grains that initiate epitaxially under steep temperature gradients and rapid solidification conditions. These unique microstructures partially account for the massive property disparity existing between AM conventionally processed alloys. Although equiaxed desirable isotropic mechanical behavior, columnar-to-equiaxed transition remains difficult to predict conventional processes, much more so AM. In this...
In situ optical absorptivity measurements are carried out to clarify the physics of laser‐material interactions involved and validate both finite element analytical models describing laser powder bed fusion processing. Absorption energy is evaluated directly using precise calorimetry compared melt pool depths for common structural metal alloys (Ti‐6Al‐4V, Inconel 625, stainless steel 316L) as a function incident power, scan velocity beam diameter. Changes in all materials found vary strongly...
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...
Gaussian laser intensity profiles are standard in laser-based metal additive manufacturing, although recent work single-layer melt tracks showed that beam shaping could offer a feasible route towards microstructural control. Since thermal cycling and grain orientation templating multilayer builds can alter microstructures, we compare three-dimensional 316 L stainless steel cubes built using elliptical profiles. Microstructural characterization confirms beams result modified improved...
High thermal gradients and complex melt pool instabilities involved in powder bed fusion–based metal additive manufacturing using focused Gaussian-shaped beams often lead to high porosity, poor morphological quality, degraded mechanical performance. We show here that Bessel offer unprecedented control over the spatiotemporal evolution of stainless steel (SS 316L) comparison Gaussian beams. Notably, nondiffractive nature enables greater tolerance for focal plane positioning during 3D...
Pitting corrosion in seawater is one of the most difficult forms to identify and control. A workhorse material for marine applications, 316L stainless steel (316L SS) known balance resistance pitting with good mechanical properties. The advent additive manufacturing (AM), particularly laser powder bed fusion (LPBF), has prompted numerous microstructural investigations LPBF SS; however, origins on as-built surfaces unknown, despite their utmost importance certification SS prior fielding....
Laser melting technologies in welding and additive manufacturing, such as laser powder bed fusion, promises to revolutionize manufacturing. However, a challenge remains preventing pore defects produced by melt pool instabilities, which degrade part quality. Using X-ray imaging synchronized with ultrahigh-speed (40 ns) absorption radiometry coupled high-fidelity simulations, we discovered that periodic oscillations the pool's morphology existed prior transition chaotic pore-generating...