scholarly journals A Novel Classification Method for Pores in Laser Powder Bed Fusion

Metals ◽  
2021 ◽  
Vol 11 (12) ◽  
pp. 1912
Author(s):  
Natan Nudelis ◽  
Peter Mayr
Keyword(s):  
Essential Element ◽  
Cylindrical Sample ◽  
Classification Method ◽  
Powder Bed Fusion ◽  
Laser Powder Bed Fusion ◽  
Pore Characteristics ◽  
Element Analysis ◽  
Powder Bed ◽  
X Ray ◽  
Current State

Nowadays, additive manufacturing (AM) using laser powder bed fusion (LPBF) is acknowledged for its ability to generate near-net-shape components for various industries such as aerospace, automotive, and health industries. However, internal defects seem to be the inevitable concomitant in the current state of laser powder bed fusion of Al alloys. Hence, knowledge of the formation, different types, and morphologies of pores and their suppression is an essential element for successful future AM applications. The purpose of this research is to qualify a new approach of defect classification using X-ray tomography. In this framework, this research examined the influence of size, shape, and location of pores on crack initiation for AlSi10Mg parts produced by LPBF. For this reason, a total number of 39,228 pores detected in a cylindrical sample were categorised. Additionally, 26 selected pores of different morphology from the X-ray scan were analysed by means of finite element analysis (FEA). Moreover, fracture mechanics determinations were carried out to examine the correlations between pore characteristics and degree of stress concentration. The result is an evaluated novel pore classification method that can be used for process adjustments, quality assurance, as well as further research.

scholarly journals In Situ Analysis of Laser Powder Bed Fusion Using Simultaneous High-Speed Infrared and X-ray Imaging

JOM ◽  
2020 ◽  
Vol 73 (1) ◽  
pp. 201-211 ◽  
Author(s):  
Benjamin Gould ◽  
Sarah Wolff ◽  
Niranjan Parab ◽  
Cang Zhao ◽  
Maria Cinta Lorenzo-Martin ◽  
...  
Keyword(s):  
High Speed ◽  
In Situ Analysis ◽  
Powder Bed Fusion ◽  
Laser Powder Bed Fusion ◽  
Powder Bed ◽  
X Ray ◽  
X Ray Imaging

Characterization of channels made by laser powder bed fusion and binder jetting using X-ray CT and image analysis

2020 ◽  
Vol 36 ◽  
pp. 101445
Author(s):  
T. Dahmen ◽  
C.G. Klingaa ◽  
S. Baier-Stegmaier ◽  
A. Lapina ◽  
D.B. Pedersen ◽  
...  
Keyword(s):  
Image Analysis ◽  
Powder Bed Fusion ◽  
Laser Powder Bed Fusion ◽  
Powder Bed ◽  
X Ray ◽  
Binder Jetting

scholarly journals Synchrotron Characterisation of Ultra-Fine Grain TiB2/Al-Cu Composite Fabricated by Laser Powder Bed Fusion

2021 ◽  
Author(s):  
Sheng Li ◽  
Biao Cai ◽  
Ranxi Duan ◽  
Lei Tang ◽  
Zihan Song ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Tensile Loading ◽  
Fusion Pore ◽  
Powder Bed Fusion ◽  
Laser Powder Bed Fusion ◽  
Powder Bed ◽  
X Ray ◽  
Random Texture ◽  
Average Grain Size

AbstractIsotropy in microstructure and mechanical properties remains a challenge for laser powder bed fusion (LPBF) processed materials due to the epitaxial growth and rapid cooling in LPBF. In this study, a high-strength TiB2/Al-Cu composite with random texture was successfully fabricated by laser powder bed fusion (LPBF) using pre-doped TiB2/Al-Cu composite powder. A series of advanced characterisation techniques, including synchrotron X-ray tomography, correlative focussed ion beam–scanning electron microscopy (FIB-SEM), scanning transmission electron microscopy (STEM), and synchrotron in situ X-ray diffraction, were applied to investigate the defects and microstructure of the as-fabricated TiB2/Al-Cu composite across multiple length scales. The study showed ultra-fine grains with an average grain size of about 0.86 μm, and a random texture was formed in the as-fabricated condition due to rapid solidification and the TiB2 particles promoting heterogeneous nucleation. The yield strength and total elongation of the as-fabricated composite were 317 MPa and 10%, respectively. The contributions of fine grains, solid solutions, dislocations, particles, and Guinier–Preston (GP) zones were calculated. Failure was found to be initiated from the largest lack-of-fusion pore, as revealed by in situ synchrotron tomography during tensile loading. In situ synchrotron diffraction was used to characterise the lattice strain evolution during tensile loading, providing important data for the development of crystal-plasticity models.

scholarly journals Transition mechanism of melt depth during Laser Powder Bed Fusion using in-situ X-ray and thermal imaging

2021 ◽  
Author(s):  
Tomoya Ogura ◽  
Yuki Wakai ◽  
Shizuka Nakano ◽  
Naoko Sato ◽  
Satoshi Kajino ◽  
...  
Keyword(s):  
Laser Irradiation ◽  
Thermal Imaging ◽  
Driving Force ◽  
Powder Bed Fusion ◽  
Laser Powder Bed Fusion ◽  
Molten Droplet ◽  
Recoil Pressure ◽  
Powder Bed ◽  
X Ray ◽  
Transition Mechanism

Abstract This research clarified the transition mechanism of melt depth in Ti powder bed during Laser Powder Bed Fusion process using in-situ X-ray and thermal imaging. A fiber laser beam of 150 W was irradiated on a powder bed at a scan speed of 15 mm/s for 3.5 s in a vacuum chamber. The obtained X-ray images showed a keyhole depth Ld increased immediately after laser irradiation, gradually decreased, and became constant. It also showed a keyhole width Lw increased immediately after laser irradiation and decreased afterward, after that, Lw increased again, and became constant. Furthermore, thermal images that measured the temperature on the powder bed showed the high temperature width Lh gradually increased and become constant. The model of the driving force which pushed the molten droplet was examined by analyzing the volume and scattering speed of the molten droplet. The model indicated the recoil pressure caused by the vaporization of powder metal was a driving force for the molten droplet scattering. The transition mechanism of keyhole depth was considered as follows. The increase of Ld at the beginning is due to the increase of the recoil pressure PT. This is because the decrease of Lw and large quantity of vaporization. Next, the decrease of Ld is due to the decrease in PT. This is because the increase of Lw and decrease of quantity of vaporization. At last, the transition to the constant Ld is caused by stabilization of Lw and Lh followed by stabilization of PT.

scholarly journals Microstructure Evolution of FeNiCoCrAl1.3Mo0.5 High Entropy Alloy during Powder Preparation, Laser Powder Bed Fusion, and Microplasma Spraying

Materials ◽  
2021 ◽  
Vol 14 (24) ◽  
pp. 7870
Author(s):  
Anton Semikolenov ◽  
Pavel Kuznetsov ◽  
Tatyana Bobkova ◽  
Svetlana Shalnova ◽  
Olga Klimova-Korsmik ◽  
...  
Keyword(s):  
Solid Solution ◽  
Phase Composition ◽  
Cast Alloy ◽  
High Entropy Alloy ◽  
Gas Atomization ◽  
Face Centered Cubic ◽  
Powder Bed Fusion ◽  
Laser Powder Bed Fusion ◽  
Powder Bed ◽  
X Ray

In the present study, powder of FeCoCrNiMo0.5Al1.3 HEA was manufactured by gas atomization process, and then used for laser powder bed fusion (L-PBF) and microplasma spraying (MPS) technologies. The processes of phase composition and microstructure transformation during above mentioned processes and subsequent heat treatment were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), and differential thermal analysis (DTA) methods. It was found that gas atomization leads to a formation of dendrites of body centered cubic (BCC) supersaturated solid solution with insignificant Mo-rich segregations on the peripheries of the dendrites. Annealing leads to an increase of element segregations till to decomposition of the BCC solid solution and formation of σ-phase and B2 phase. Microstructure and phase composition of L-PBF sample are very similar to those of the powder. The MPS coating has a little fraction of face centered cubic (FCC) phase because of Al oxidation during spraying and formation of regions depleted in Al, in which FCC structure becomes more stable. Maximum hardness (950 HV) is achieved in the powder and L-PBF samples after annealing at 600 °C. Elastic modulus of the L-PBF sample, determined by nanoindentation, is 165 GPa, that is 12% lower than that of the cast alloy (186 GPa).

scholarly journals Cooling dynamics of two titanium alloys during laser powder bed fusion probed with in situ X-ray imaging and diffraction

2020 ◽  
Vol 195 ◽  
pp. 108987
Author(s):  
Nicholas P. Calta ◽  
Vivek Thampy ◽  
Duncan R.C. Lee ◽  
Aiden A. Martin ◽  
Rishi Ganeriwala ◽  
...  
Keyword(s):  
Titanium Alloys ◽  
Powder Bed Fusion ◽  
Laser Powder Bed Fusion ◽  
Powder Bed ◽  
X Ray ◽  
X Ray Imaging
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