scholarly journals Effect of the Melt Pool Boundary Network on the Anisotropic Mechanical Properties of Selective Laser Melted 304L

2021 ◽  
Vol 5 (4) ◽  
pp. 110
Author(s):  
Myranda Spratt ◽  
Joseph W. Newkirk ◽  
Okanmisope Fashanu ◽  
K. Chandrashekhara
Keyword(s):  
Mechanical Properties ◽  
Numerical Models ◽  
304L Stainless Steel ◽  
Compressive Properties ◽  
Laser Melting ◽  
Boundary Concentration ◽  
Melt Pool ◽  
Anisotropic Mechanical Properties ◽  
Anisotropic Plastic ◽  
Weak Negative Correlation

Anisotropic mechanical properties are a well-known issue in selective laser melted parts. The microstructure produced by selective laser melting (SLM) is directional, including the solidified melt pool structures and grains. This work investigates the melt pool boundary’s effects on 304L stainless steel’s compressive properties. 304L stainless steel solid cylinders were built using a pulse laser SLM machine in four directions using three hatch angle rotations: 0°, 67°, and 105°. The twelve samples were compression tested, and the results were analyzed. Numerical models were also created with the different hatch angles and directions. The melt pool boundary network (MPBN) in each build was tracked using the model across multiple planes. Results showed that both the hatch angle and build orientation influenced the concentration of melt pool boundaries present in the manufactured samples. A weak negative correlation of compressive strength to the melt pool boundaries’ concentration was also observed, indicating that the melt pool boundary concentration negatively affected the material’s strength. Local anisotropic plastic deformation was also observed in some of the compressed samples. In those samples, it was observed that directions that plastically deformed more also contained higher concentration of the melt pool boundaries.

scholarly journals Effect of process parameters on the microstructure and mechanical properties of AA2024 fabricated using selective laser melting

2020 ◽  
Vol 112 (1-2) ◽  
pp. 175-192
Author(s):  
Mulla Ahmet Pekok ◽  
Rossitza Setchi ◽  
Michael Ryan ◽  
Quanquan Han ◽  
Dongdong Gu
Keyword(s):  
Mechanical Properties ◽  
Selective Laser Melting ◽  
Scanning Speed ◽  
High Energy ◽  
Incomplete Fusion ◽  
Laser Melting ◽  
Melt Pool ◽  
2024 Alloy ◽  
Manufacturing Techniques ◽  
Melt Pool Size

AbstractSelective laser melting (SLM) offers significant benefits, including geometric freedom and rapid production, when compared with traditional manufacturing techniques. However, the materials available for SLM production remain limited, restricting the industrial adoption of the technology. The mechanical properties and microstructure of many aluminium alloys have not been fully explored, as their manufacturability using SLM is extremely challenging. This study investigates the effect of laser power, hatch spacing and scanning speed on the mechanical and microstructural properties of as-fabricated aluminium 2024 alloy (AA2024) manufactured using SLM. The results reveal that almost crack-free structures with high relative density (99.9%) and Archimedes density (99.7%) have been achieved. It is shown that when using low energy density (ED) levels, large cracks and porosities are a major problem, owing to incomplete fusion; however, small gas pores are prevalent at high-energy densities due to the dissolved gas particles in the melt pool. An inversely proportional relationship between ED and microhardness has also been observed. Lower ED decreases the melt pool size and temperature gradients but increases the cooling rate, creating a fine-grained microstructure, which restricts dislocation movement, therefore increasing the microhardness. The highest microhardness (116 HV0.2), which was obtained from one of the lowest EDs used (100 J/mm3), is 45% higher than as-cast AA2024-0, but 17% lower than wrought AA2024-T6 alloy.

scholarly journals An investigation of the anisotropic properties of heat-treated maraging steel grade 300 processed by laser powder bed fusion

2021 ◽  
Author(s):  
Even W. Hovig ◽  
Amin S. Azar ◽  
Klas Solberg ◽  
Knut Sørby
Keyword(s):  
Mechanical Properties ◽  
Tensile Properties ◽  
Maraging Steel ◽  
Image Correlation ◽  
Powder Bed Fusion ◽  
Material Models ◽  
Powder Bed ◽  
Melt Pool ◽  
Heat Treated ◽  
Anisotropic Mechanical Properties

AbstractIn order to explore the possibilities enabled by laser beam powder bed fusion of metals (PBF-LB/M), reliable material models are necessary to optimize designs with respect to weight and stiffness. Due to the unique processing conditions in PBF-LB/M, materials often develop a dominating microstructure that leads to anisotropic mechanical properties, and thus isotropic material models fail to account for the orientation-dependent mechanical properties. To investigate the anisotropy of 18Ni300 maraging steel, tensile specimens were built in seven different orientations. The specimens were heat treated at two different conditions and tested for their tensile properties using digital image correlation (DIC) technique. The microstructure and fracture surfaces are investigated with scanning electron microscope and electron backscatter diffraction. The tensile properties are typical for the material, with a yield strength in the range of 1850 MPa to 1950 MPa, and ultimate tensile strength in the range of 1900 MPa to 2000 MPa. The elastic modulus is 180 GPa, and the elongation at fracture is in the range of 2–6% for all specimens. The strain fields analysed with DIC reveals anisotropic straining in both the elastic and plastic parts of the flow curve for both direct ageing and solution treatment plus ageing specimens. In the former condition, the elastic anisotropy is dictated by the fraction of melt pool boundaries on the transverse surfaces of the specimens. When the material is solution treated prior to ageing, the melt pool boundary effect was supressed.

scholarly journals An Investigation of the Anisotropic Properties of Heat-Treated Maraging Steel Grade 300 Processed by Laser Powder Bed Fusion

2021 ◽  
Author(s):  
Even Wilberg Hovig ◽  
Amin S Azar ◽  
Klas Solberg ◽  
Knut Sørby
Keyword(s):  
Mechanical Properties ◽  
Tensile Properties ◽  
Maraging Steel ◽  
Image Correlation ◽  
Powder Bed Fusion ◽  
Material Models ◽  
Powder Bed ◽  
Melt Pool ◽  
Heat Treated ◽  
Anisotropic Mechanical Properties

Abstract In order to explore the possibilities enabled by laser beam powder bed fusion of metals (PBF-LB/M), reliable material models are necessary to optimize designs with respect to weight and stiffness. Due to the unique processing conditions in PBF-LB/M, materials often develop a dominating microstructure that leads to anisotropic mechanical properties, and thus isotropic material models fail to account for the orientation-dependent mechanical properties. To investigate the anisotropy of 18Ni300 maraging steel, tensile specimens were built in seven different orientations. The specimens were heat treated at two different conditions and tested for their tensile properties using digital image correlation (DIC) technique. The microstructure and fracture surfaces are investigated with scanning electron microscope and electron backscatter diffraction. The tensile properties are typical for the material, with a yield strength in the range of 1850 MPa to 1950 MPa, and ultimate tensile strength in the range of 1900 MPa to 2000 MPa. The elastic modulus is 180 GPa, and the elongation at fracture is in the range of 2-6% for all specimens. The strain fields analysed with DIC reveals anisotropic straining in both the elastic and plastic parts of the flow curve for both direct ageing and solution treatment plus ageing specimens. In the former condition, the elastic anisotropy is dictated by the fraction of melt pool boundaries on the transverse surfaces of the specimens. When the material is solution treated prior to ageing, the melt pool boundary effect was supressed.

scholarly journals Numerical Investigation of Thermo-Mechanical Field during Selective Laser Melting Process with Experimental Validation

Metals ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 1003
Author(s):  
Lan Li ◽  
Frank Liou
Keyword(s):  
Stainless Steel ◽  
Selective Laser Melting ◽  
Thermal Stresses ◽  
Pool Size ◽  
Solidification Structure ◽  
Temperature History ◽  
304L Stainless Steel ◽  
Laser Melting ◽  
Melt Pool ◽  
Melt Pool Size

In this study, thermo-mechanical simulation was conducted to predict thermal and stress behavior in Selective Laser Melting (SLM). Temperature-dependent material properties for processed material 304L stainless steel were incorporated into the model in order to capture the change from powder to fully dense solid stainless steel. Temperature and thermal stress history were tracked under conditions of different parameter sets which were designed to reduce defect formation. The thermal model predicted the temperature history for multi-track scans under different process parameters, such as laser power, effective scanning speed and hatch spacing. Subsequently, the corresponding melt-pool size, solidification rate and temperature gradients could be calculated from simulated temperature data. These three parameters from the simulation were compared with experimental melt pool size, grain structure and cell spacing data obtained from a Renishaw AM250. The experimental data were also used to determine unknown simulation parameters required by the continuum model, e.g., the optical penetration depth and thermal conductivity multiplier for the molten region. This allowed the simulation model to accurately predict melt pool size and solidification structure of SLM 304L stainless steel. Simulated stress showed that the subsequent thermal cyclic melting in successive scanned tracks resulted in alternating compressive and tensile thermal stresses. This work will provide insight for studying microstructure morphology, residual stress and deformations in the SLM process of 304L stainless steel.

scholarly journals On the Anisotropic Mechanical Properties of Selective Laser Melted Stainless Steel

2017 ◽  
Author(s):  
Leonhard Hitzler ◽  
Johann Hirsch ◽  
Burkhard Heine ◽  
Markus Merkel ◽  
Wayne Hall ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Stainless Steel ◽  
Material Properties ◽  
Raw Material ◽  
Layer Versus ◽  
Laser Melting ◽  
Freeform Fabrication ◽  
Precise Knowledge ◽  
Anisotropic Mechanical Properties ◽  
A Current

The thorough description of the peculiarities of additively manufactured structures represents a current challenge for aspiring freeform fabrication methods, such as the selective laser melting (SLM). All of which have an immense advantage in the fast fabrication (no special tooling or moulds required), the geometrical flexibility in the design of components, and their efficiency when only low quantities are required. However, designs demand the precise knowledge of the material properties, which in case of additively manufactured structures are anisotropic and, under certain circumstances, in addition of an inhomogeneous nature. Furthermore, these characteristics are highly dependent on the fabrication settings. Within this study, the anisotropic tensile properties of selective laser melted stainless steel (1.4404, 316L) are investigated: The Young’s modulus ranged from 148 GPa to 227 GPa, the ultimate tensile strength from 512 MPa to 699 MPa and the breaking elongation ranged, respectively, from 12% to 43%. The results were compared to related studies, in order to classify the influence of the fabrication settings. Furthermore, the influence of the chosen raw material was addressed by comparing deviations on the directional dependencies reasoned by differing microstructural developments during manufacture. Stainless steel was found to possess its maximum strength at a 45° layer versus loading offset, which is precisely where AlSi10Mg was previously reported to be at its weakest.

scholarly journals Nonlinear modelling of the seismic response of masonry structures: Calibration strategies

2021 ◽  
Author(s):  
Antonio Maria D’Altri ◽  
Francesco Cannizzaro ◽  
Massimo Petracca ◽  
Diego Alejandro Talledo
Keyword(s):  
Mechanical Properties ◽  
Numerical Models ◽  
Shear Stiffness ◽  
Model Material ◽  
National Standards ◽  
National Standard ◽  
Masonry Structures ◽  
Nonlinear Modelling ◽  
Various Boundary Conditions ◽  
Panel Stiffness

AbstractIn this paper, a simple and practitioners-friendly calibration strategy to consistently link target panel-scale mechanical properties (that can be found in national standards) to model material-scale mechanical properties is presented. Simple masonry panel geometries, with various boundary conditions, are utilized to test numerical models and calibrate their mechanical properties. The calibration is successfully conducted through five different numerical models (most of them available in commercial software packages) suitable for nonlinear modelling of masonry structures, using nonlinear static analyses. Firstly, the panel stiffness calibration is performed, focusing the attention to the shear stiffness. Secondly, the panel strength calibration is conducted for several axial load ratios by attempts using as reference the target panel strength deduced by well-known analytical strength criteria. The results in terms of panel strength for the five different models show that this calibration strategy appears effective in obtaining model properties coherent with Italian National Standard and Eurocode. Open issues remain for the calibration of the post-peak response of masonry panels, which still appears highly conventional in the standards.

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