scholarly journals Numerical Study on Effect of the Building Height and Material Properties on Thermal Distortion of Large Cylinders Manufactured through Laser Powder Bed Fusion

2021 ◽  
Author(s):  
Seulbi Lee ◽  
Tae Yang Bang ◽  
Woojong Kim ◽  
Mincheol Kang ◽  
Yoon Suk Choi
Keyword(s):  
Material Properties ◽  
Numerical Study ◽  
Thermal Distortion ◽  
Powder Bed Fusion ◽  
Laser Powder Bed Fusion ◽  
Powder Bed ◽  
Building Height

scholarly journals Effects of Positioning Conditions on Material Properties In Powder bed Fusion Additive Manufacturing

2021 ◽  
Author(s):  
Mevlüt Yunus Kayacan ◽  
Nihat Yılmaz
Keyword(s):  
Additive Manufacturing ◽  
Material Properties ◽  
Layer By Layer ◽  
Powder Bed Fusion ◽  
Laser Powder Bed Fusion ◽  
Cooling Rates ◽  
Powder Bed ◽  
Manufacturing Technologies ◽  
Average Size ◽  
Hardness Values

Abstract Among additive manufacturing technologies, Laser Powder Bed Fusion (L-PBF) is considered the most widespread layer-by-layer process. Although the L-PBF, which is also called as SLM method, has many advantages, several challenging problems must be overcome, including part positioning issues. In this study, the effect of part positioning on the microstructure of the part in the L-PBF method was investigated. Five Ti6Al4V samples were printed in different positions on the building platform and investigated with the aid of temperature, porosity, microstructure and hardness evaluations. In this study, martensitic needles were detected within the microstructure of Ti6Al4V samples. Furthermore, some twins were noticed on primary martensitic lines and the agglomeration of β precipitates was observed in vanadium rich areas. The positioning conditions of samples were revealed to have a strong effect on temperature gradients and on the average size of martensitic lines. Besides, different hardness values were attained depending on sample positioning conditions. As a major result, cooling rates were found related to positions of samples and the location of point on the samples. Higher cooling rates and repetitive cooling cycles resulted in microstructures becoming finer and harder.

scholarly journals Numerical study of the impact of vaporisation on melt pool dynamics in Laser Powder Bed Fusion - Application to IN718 and Ti–6Al–4V

2020 ◽  
Vol 35 ◽  
pp. 101249
Author(s):  
Alexis Queva ◽  
Gildas Guillemot ◽  
Clara Moriconi ◽  
Charlotte Metton ◽  
Michel Bellet
Keyword(s):  
Numerical Study ◽  
Powder Bed Fusion ◽  
Laser Powder Bed Fusion ◽  
Powder Bed ◽  
Melt Pool ◽  
The Impact

Evaluation of the Material Properties of the Ti and CoCr Alloys Prepared by Laser Powder Bed Fusion

2020 ◽  
Vol 985 ◽  
pp. 223-228
Author(s):  
Jana Bidulská ◽  
Róbert Bidulský ◽  
Patrik Petrouse ◽  
Tibor Kvačkaj ◽  
Marco Actis Grande ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Image Analysis ◽  
Additive Manufacturing ◽  
Material Properties ◽  
Ti6al4v Alloy ◽  
Homogeneous Distribution ◽  
Powder Bed Fusion ◽  
Laser Powder Bed Fusion ◽  
Powder Bed ◽  
Quantitative Image

The main aim of the present paper is evaluated the mechanical properties, microstructures and porosity of Ti6Al4V and CoCrW alloys produced by Laser Powder Bed Fusion (L-PBF) as an additive manufacturing (AM) technology. The mechanical properties were follows: For Ti6Al4V alloy the UTS was 1180 MPa; the YS was in the range <600; 745 MPa>. For CoCrW alloys, the UTS were in range <750; 950 MPa> and YS was in range <400; 500>. Evaluation of porosity was realized on non-etched samples using by quantitative image analysis in order to describe the dimensional and morphological porosity characteristics. The pores in the Ti6Al4V alloy showed homogeneous distribution without significant large pores.

A Numerical Study on the Keyhole Formation During Laser Powder Bed Fusion Process

2019 ◽  
Vol 141 (10) ◽  
Author(s):  
Subin Shrestha ◽  
Y. Kevin Chou
Keyword(s):  
Energy Density ◽  
Numerical Study ◽  
High Energy ◽  
High Energy Density ◽  
Computational Domain ◽  
Powder Bed Fusion ◽  
Laser Powder Bed Fusion ◽  
Powder Bed ◽  
Melt Pool ◽  
Keyhole Behavior

The dynamic phenomenon of a melt pool during the laser powder bed fusion (LPBF) process is complex and sensitive to process parameters. As the energy density input exceeds a certain threshold, a huge vapor depression may form, known as the keyhole. This study focuses on understanding the keyhole behavior and related pore formation during the LPBF process through numerical analysis. For this purpose, a thermo-fluid model with discrete powder particles is developed. The powder distribution, obtained from a discrete element method (DEM), is incorporated into the computational domain to develop a 3D process physics model using flow-3d. The melt pool formation during the conduction mode and the keyhole mode of melting has been discerned and explained. The high energy density leads to the formation of a vapor column and consequently pores under the laser scan track. Further, the keyhole shape resulted from different laser powers and scan speeds is investigated. The numerical results indicated that the keyhole size increases with the increase in the laser power even with the same energy density. The keyhole becomes stable at a higher power, which may reduce the occurrence of pores during laser scanning.

scholarly journals Physics-Based Predictive Model of Lack-of-Fusion Porosity in Laser Powder Bed Fusion Considering Cap Area

Crystals ◽  
2021 ◽  
Vol 11 (12) ◽  
pp. 1568
Author(s):  
Wenjia Wang ◽  
Steven Y. Liang
Keyword(s):  
Image Analysis ◽  
Cross Section ◽  
Void Fraction ◽  
Material Properties ◽  
Molten Pool ◽  
Analytical Modeling ◽  
Powder Bed Fusion ◽  
Laser Powder Bed Fusion ◽  
Powder Bed ◽  
Lack Of Fusion

This work proposed a computationally efficient analytical modeling strategy to calculate the product porosity in laser powder bed fusion (LPBF) induced by a lack-of-fusion defect, with the consideration of cap area in solidified molten pools, influence of powder bed characteristics on material properties, and un-melted powders in the lack-of-fusion portion. The powder packing pattern and powder bed void fraction were estimated by an advancing front method and the technique of image analysis. The effects of powder bed characteristics on the material properties were considered by analytical models with solid properties and powder bed void fraction as inputs. A physics-based thermal model was utilized to calculate the temperature distribution and molten pool size. The molten pool cross section in transvers direction was assumed to be dual half-elliptical. Based on this assumption and molten pool size, the geometry of the molten pool cross section with cap area was determined. The overlapping pattern of molten pools in adjacent scan tracks and layers was then obtained with given hatch space and layer thickness. The lack-of-fusion area fraction was obtained through image analysis of the overlapping pattern. The lack-of-fusion porosity was the multiplication of the lack-of-fusion area fraction and powder bed void fraction. The predictions of porosity under different process conditions were compared with experimental results of 316L stainless steel and showed a better predictive accuracy than the predictions that did not consider cap area. The proposed analytical modeling method has no numerical calculations, which ensures its low computational cost. Thus, the proposed model can be a convenient tool for the fast computation of lack-of-fusion-induced porosity and can help the quality control in LPBF.

A Numerical Study on the Keyhole Formation During Laser Powder Bed Fusion Process

2019 ◽  
Author(s):  
Subin Shrestha ◽  
Y. Kevin Chou
Keyword(s):  
Energy Density ◽  
Numerical Study ◽  
High Energy ◽  
High Energy Density ◽  
Computational Domain ◽  
Powder Bed Fusion ◽  
Laser Powder Bed Fusion ◽  
Powder Bed ◽  
Melt Pool ◽  
Keyhole Behavior

Abstract The dynamic phenomenon of a melt pool during the laser powder bed fusion (LPBF) process is complex and sensitive to process parameters. As the energy density input exceeds a certain threshold, a huge vapor depression may form, known as the keyhole. This study focuses on understanding the keyhole behavior and related pore formation during the LPBF process through numerical analysis. For this purpose, a thermo-fluid model with discrete powder particles is developed. The powder distribution, obtained from a discrete element method (DEM), is incorporated into the computational domain to develop a 3D process physics model using FLOW-3D. The melt pool formation during the conduction mode and the keyhole mode of melting has been discerned and explained. The high energy density leads to the formation of a vapor column and consequently pores under the laser scan track. Further, the keyhole shape resulted from different laser powers and scan speeds is investigated. The numerical results indicated that the keyhole size increases with the increase in the laser power even with the same energy density. The keyhole becomes stable at a higher power, which may reduce the occurrence of pores during laser scanning.

scholarly journals Unravelling the multi-scale structure–property relationship of laser powder bed fusion processed and heat-treated AlSi10Mg

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
P. Van Cauwenbergh ◽  
V. Samaee ◽  
L. Thijs ◽  
J. Nejezchlebová ◽  
P. Sedlák ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Grain Refinement ◽  
Rapid Solidification ◽  
Material Properties ◽  
Mechanical And Thermal Properties ◽  
Powder Bed Fusion ◽  
Structure Property ◽  
Laser Powder Bed Fusion ◽  
Powder Bed ◽  
Heat Treated

AbstractTailoring heat treatments for Laser Powder Bed Fusion (LPBF) processed materials is critical to ensure superior and repeatable material properties for high-end applications. This tailoring requires in-depth understanding of the LPBF-processed material. Therefore, the current study aims at unravelling the threefold interrelationship between the process (LPBF and heat treatment), the microstructure at different scales (macro-, meso-, micro-, and nano-scale), and the macroscopic material properties of AlSi10Mg. A similar solidification trajectory applies at different length scales when comparing the solidification of AlSi10Mg, ranging from mould-casting to rapid solidification (LPBF). The similarity in solidification trajectories triggers the reason why the Brody-Flemings cellular microsegregation solidification model could predict the cellular morphology of the LPBF as-printed microstructure. Where rapid solidification occurs at a much finer scale, the LPBF microstructure exhibits a significant grain refinement and a high degree of silicon (Si) supersaturation. This study has identified the grain refinement and Si supersaturation as critical assets of the as-printed microstructure, playing a vital role in achieving superior mechanical and thermal properties during heat treatment. Next, an electrical conductivity model could accurately predict the Si solute concentration in LPBF-processed and heat-treated AlSi10Mg and allows understanding the microstructural evolution during heat treatment. The LPBF-processed and heat-treated AlSi10Mg conditions (as-built (AB), direct-aged (DA), stress-relieved (SR), preheated (PH)) show an interesting range of superior mechanical properties (tensile strength: 300–450 MPa, elongation: 4–13%) compared to the mould-cast T6 reference condition.

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