In situ X-ray imaging of defect and molten pool dynamics in laser additive manufacturing

Leung, Chu Lun Alex; Marussi, Sebastian; Atwood, Robert C.; Towrie, Michael; Withers, Philip J.; Lee, Peter

doi:10.1038/s41467-018-03734-7

Cited by 601 publications

(300 citation statements)

References 63 publications

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“…The figure clearly shows the presence of voids in the internal structure of the lattice. In fact, the laser‐powder interaction and solidification phenomena of the laser additive manufacturing process have been investigated through in situ and operando high‐speed synchrotron X‐ray imaging . The study provided interesting physical insights into the solidification phenomena and developed mechanism maps for predicting the evolution of melt features.…”

Section: Manufacturability Of Tpms‐based Metamaterialsmentioning

confidence: 99%

Multifunctional Mechanical Metamaterials Based on Triply Periodic Minimal Surface Lattices

2019

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In nature, cellular materials exhibit enhanced multifunctionalities driven mainly by their sophisticated topologies and length scales. These natural systems have inspired the development and expansion of synthetic architected materials for revolutionary applications. Consequently, both the design and synthesis techniques gained considerable attention and have massively progressed over the last few decades. Such materials with topology-controlled properties are commonly known as "metamaterials." Architected materials with topologies based on triply periodic minimal surfaces (TPMS) which are of particular interest have attracted much attention recently due to their mathematically controlled fascinating topologies and their exhibited physical and mechanical properties. Herein, the design, synthesis, and use of TPMS in the field of metamaterials and metacomposites for several applications are focused upon. The design process to create TPMS-based 3D lattices is summarized and the different manufacturing processes used to fabricate these lattices are highlighted. Herein, the materialtopology-mechanical properties relationship of different TPMS-based lattices that are investigated in the literature is discussed. A further objective is to highlight the applications where TPMS-based lattices or composites can be efficiently used as well as the research areas to be explored. development of macro/micro/nanomechanics-based constitutive models and computational tools that can be used effectively in guiding the design of advanced materials. He is particularly active in using digital design and 3D printing for creating multifunctional architected materials and composites for various applications.

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Section: Manufacturability Of Tpms‐based Metamaterialsmentioning

confidence: 99%

Multifunctional Mechanical Metamaterials Based on Triply Periodic Minimal Surface Lattices

2019

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“…Over the last few decades, the research community, through its endeavors, has been expanding our knowledge of the formation, development, and controls of laser spattering [13,14]. A few mechanisms were proposed to explain the laser-spattering phenomenon, which are mostly concerned with the local laser energy absorption, vapor plume dynamics, and melt flow [15,16].…”

Section: Introductionmentioning

confidence: 99%

Bulk-Explosion-Induced Metal Spattering During Laser Processing

Zhao

Guo

et al. 2019

Phys. Rev. X

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Spattering has been a problem in metal processing involving high-power lasers, like laser welding, machining, and recently, additive manufacturing. Limited by the capabilities of in situ diagnostic techniques, typically imaging with visible light or laboratory x-ray sources, a comprehensive understanding of the laser-spattering phenomenon, particularly the extremely fast spatters, has not been achieved yet. Here, using MHz single-pulse synchrotron-x-ray imaging, we probe the spattering behavior of Ti-6Al-4V with micrometer spatial resolution and subnanosecond temporal resolution. Combining direct experimental observations, quantitative image analysis, as well as numerical simulations, our study unravels a novel mechanism of laser spattering: The bulk explosion of a tonguelike protrusion forming on the front keyhole wall leads to the ligamentation of molten metal at the keyhole rims and the subsequent spattering. Our study confirms the critical role of melt and vapor flow in the laser-spattering process and opens a door to manufacturing spatter-and defect-free metal parts via precise control of keyhole dynamics.

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“…In the LPBF-based methods, the formation of defects depends on the wetting of molten pool, which is governed by the two critical process parameters: (i) laser power and (ii) scan speed. As such, increasing laser power provides more energy for powder consolidation whilst improving molten pool wetting and decreasing scan speed increases the laser-matter interaction time, making the movement of the liquid metal less violent [42,43]. Thus, a trade-off between the scan speed and laser power is required to achieve the appropriate range of molten pool temperature/wetting, i.e., the "Forming zone" in Fig.…”

Section: Slm Process Map For We43mentioning

confidence: 99%

A detailed microstructural and corrosion analysis of an additively manufactured magnesium alloy produced by selective laser melting

Esmaily¹,

Zeng²,

Mortazavi³

et al. 2020

Preprint

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Magnesium (Mg) alloys have promising potentials for lightweight and biomedical applications. Although there has been a recent interest in producing Mg alloys (including AZ, ZK and WE series) using additive manufacturing (AM), the process-structure-corrosion properties relationships in AM Mg alloys are yet to be understood. Herein, the production of Mg alloy WE43 was achieved by selective laser melting (SLM). The alloy was investigated after SLM, hot isostatic pressing (HIP) as well as an additional solutionising heat treatment. Specimens were carefully characterised, whilst assessed and contrast relative to the conventionally cast alloy counterpart. Characterisation included detailed microstructural analysis employing analytical transmission electron microscopy, X-ray mapping, and electron backscatter diffraction, which revealed the SLM prepared specimens possess a unique microstructure comprising fine grains growing with a strong [0001] texture along the building direction. The SLM prepared specimens also revealed a low fraction of process-induced and metallurgical defects, reaching < 0.1% after optimising the SLM parameters and HIP treatment. The SLM prepared WE43 was found to be cathodically more active relative to the cast WE43 because of a fine distribution of zirconium-, yttrium- and oxygen-rich particles as well as the alterations in the chemical composition of the solid-solution matrix originating from the high cooling rates of SLM. It was revealed that the oxide particles were mainly sourced by powder and thus it is hypothesised that the corrosion of SLM prepared Mg alloys could be greatly improved once the influence of powder characteristics is further understood and controlled.

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In situ X-ray imaging of defect and molten pool dynamics in laser additive manufacturing

Cited by 601 publications

References 63 publications

Multifunctional Mechanical Metamaterials Based on Triply Periodic Minimal Surface Lattices

Multifunctional Mechanical Metamaterials Based on Triply Periodic Minimal Surface Lattices

Bulk-Explosion-Induced Metal Spattering During Laser Processing

A detailed microstructural and corrosion analysis of an additively manufactured magnesium alloy produced by selective laser melting

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