An instrument for in situ time-resolved X-ray imaging and diffraction of laser powder bed fusion additive manufacturing processes
Nicholas P. Calta,Jenny Wang,Andrew M. Kiss,Aiden A. Martin,Philip J. Depond,Gabriel M. Guss,Vivek Thampy,Anthony Y. Fong,Johanna Nelson Weker,Kevin H. Stone,Christopher J. Tassone,Matthew J. Kramer,Michael F. Toney,Anthony van Buuren,Manyalibo J. Matthews +14 more
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TLDR
A laboratory-scale LPBF test bed designed to accommodate diffraction and imaging experiments at a synchrotron X-ray source during LPBF operation is described and experimental results using Ti-6Al-4V, a widely used aerospace alloy, as a model system are presented.Abstract:
In situ X-ray-based measurements of the laser powder bed fusion (LPBF) additive manufacturing process produce unique data for model validation and improved process understanding. Synchrotron X-ray imaging and diffraction provide high resolution, bulk sensitive information with sufficient sampling rates to probe melt pool dynamics as well as phase and microstructure evolution. Here, we describe a laboratory-scale LPBF test bed designed to accommodate diffraction and imaging experiments at a synchrotron X-ray source during LPBF operation. We also present experimental results using Ti-6Al-4V, a widely used aerospace alloy, as a model system. Both imaging and diffraction experiments were carried out at the Stanford Synchrotron Radiation Lightsource. Melt pool dynamics were imaged at frame rates up to 4 kHz with a ∼1.1 μm effective pixel size and revealed the formation of keyhole pores along the melt track due to vapor recoil forces. Diffraction experiments at sampling rates of 1 kHz captured phase evolution and lattice contraction during the rapid cooling present in LPBF within a ∼50 × 100 μm area. We also discuss the utility of these measurements for model validation and process improvement.read more
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Keyhole threshold and morphology in laser melting revealed by ultrahigh-speed x-ray imaging
Ross B. Cunningham,Cang Zhao,Niranjan D. Parab,Christopher Kantzos,Joseph Pauza,Kamel Fezzaa,Tao Sun,Anthony D. Rollett +7 more
TL;DR: The direct visualization of the keyhole morphology and dynamics with high-energy x-rays shows that (i) keyholes are present across the range of power and scanning velocity used in laser powder bed fusion; and (ii) there is a well-defined threshold from conduction mode to keyhole based on laser power density.
Journal ArticleDOI
Dynamics of pore formation during laser powder bed fusion additive manufacturing.
Aiden A. Martin,Nicholas P. Calta,Saad A. Khairallah,Jenny Wang,Phillip J. DePond,Anthony Y. Fong,Vivek Thampy,Gabe Guss,Andrew M. Kiss,Kevin H. Stone,Christopher J. Tassone,Johanna Nelson Weker,Michael F. Toney,Tony van Buuren,Manyalibo J. Matthews +14 more
TL;DR: In situ X-ray imaging and finite element simulations are used to show how detrimental pores form under printing conditions and develop a strategy to suppress them and provide insight into the physics of laser-metal interaction.
Journal ArticleDOI
Critical instability at moving keyhole tip generates porosity in laser melting.
Cang Zhao,Cang Zhao,Niranjan D. Parab,Xuxiao Li,Kamel Fezzaa,Wenda Tan,Anthony D. Rollett,Tao Sun +7 more
TL;DR: High-speed x-ray imaging enables operando observation of the detailed formation process of pores in Ti-6Al-4V caused by a critical instability at the keyhole tip and finds that the boundary of the key hole porosity regime in power-velocity space is sharp and smooth, varying only slightly between the bare plate and powder bed.
Journal ArticleDOI
Pore elimination mechanisms during 3D printing of metals.
S. Mohammad H. Hojjatzadeh,Niranjan D. Parab,Wentao Yan,Qilin Guo,Lianghua Xiong,Cang Zhao,Minglei Qu,Luis I. Escano,Xianghui Xiao,Kamel Fezzaa,Wes Everhart,Tao Sun,Lianyi Chen +12 more
TL;DR: It is found that the high thermocapillary force, induced by the high temperature gradient in the laser interaction region, can rapidly eliminate pores from the melt pool during the LPBF process.
Journal ArticleDOI
The effect of powder oxidation on defect formation in laser additive manufacturing
Chu Lun Alex Leung,Chu Lun Alex Leung,Sebastian Marussi,Sebastian Marussi,Michael Towrie,Robert C. Atwood,Philip J. Withers,Peter D. Lee,Peter D. Lee +8 more
TL;DR: In this paper, the authors investigated the effects of powder oxidation on the molten pool dynamics and defect formation during laser additive manufacturing (LAM) of virgin, stored, and reused powders.
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