scholarly journals Determination of Anisotropic Mechanical Properties for Materials Processed by Laser Powder Bed Fusion

2018 ◽  
Vol 2018 ◽  
pp. 1-20 ◽  
Author(s):  
Even W. Hovig ◽  
Amin S. Azar ◽  
Frode Grytten ◽  
Knut Sørby ◽  
Erik Andreassen
Keyword(s):  
Mechanical Properties ◽  
Transversely Isotropic ◽  
Tensile Tests ◽  
Image Correlation ◽  
Powder Bed Fusion ◽  
Laser Powder Bed Fusion ◽  
Inconel 718 Alloy ◽  
Powder Bed ◽  
Anisotropic Mechanical Properties ◽  
Anisotropic Elastic

Improving the success rate in additive manufacturing and designing highly optimized structures require proper understanding of material behaviour. This study proposes a novel experimental method by which anisotropic mechanical properties of additively manufactured materials can be assessed. The procedure is based on tensile testing of flat specimens, manufactured by laser powder bed fusion (LPBF) at different orientations relative to the build plate. In this study, the procedure was applied to the Inconel 718 alloy. Three identical specimen sets were built, each of which received complementary postprocessing treatments. The tensile tests were carried out on specimens with as-built surface finish. Digital image correlation was used to record the strain field evolution on two perpendicular surfaces of the tensile specimens under loading. An optimization algorithm is also proposed for determining the anisotropic elastic constants using only a few tensile test results. It was observed that both build orientation and postprocessing have strong influence on the anisotropic mechanical properties of the material. The effect of microstructure was also investigated and characterised. Consequently, three transversely isotropic compliance matrices were constructed, representing the effect of the different processing conditions.

Laser Welding of Laser Powder Bed Fusion Manufactured Inconel 718: Microstructure and Mechanical Properties

2021 ◽  
Vol 883 ◽  
pp. 234-241
Author(s):  
Timo Rautio ◽  
Jarmo Mäkikangas ◽  
Jani Kumpula ◽  
Antti Järvenpää ◽  
Atef Hamada
Keyword(s):  
Mechanical Properties ◽  
Inconel 718 ◽  
Tensile Tests ◽  
Optical Microscope ◽  
Powder Bed Fusion ◽  
Laser Powder Bed Fusion ◽  
Inconel 718 Alloy ◽  
Powder Bed ◽  
Back Scattering ◽  
Solidification Crack

This paper focuses on the laser weldability of additively manufactured (AM) Inconel 718. The experiments of this research were conducted on different series of AM Inconel 718 alloy, i.e. as­-built, heat­ treated (HT), and HT after welding, and comprehensively characterized using optical microscope and electron back scattering diffraction (EBSD). The weld morphology and microstruc­tural evolution of the fusion zone were recorded. The mechanical properties of the welded AM Inconel 718 were evaluated by tensile tests and hardness measurements. It was found that solidification crack and micropore defects are induced in the as­built AM Inconel 718. However, defect­free weld was promoted in the HT alloy. The changes in hardness profiles and tensile strength under the experimen­tal parameters were further reported. Homogenous hardness of 500 HV across the weld was obtained when HT was applied after the LW.

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.

Microstructure and Mechanical Properties of Laser Butt Welded Laser Powder Bed Fusion Manufactured and Sheet Metal 316L Parts

2020 ◽  
Vol 861 ◽  
pp. 9-14
Author(s):  
Timo Rautio ◽  
Juho Jalava-Kanervio ◽  
Jani Kumpula ◽  
Jarmo Mäkikangas ◽  
Antti Järvenpää
Keyword(s):  
Heat Treatment ◽  
Sheet Metal ◽  
Microstructural Analysis ◽  
Tensile Tests ◽  
Butt Joint ◽  
Image Correlation ◽  
Powder Bed Fusion ◽  
Laser Powder Bed Fusion ◽  
Powder Bed ◽  
Columnar Grains

Laser weldability of dissimilar parts produced with different techniques from 316L material was studied in this paper. Butt joint welding was performed on pairs of sheet metal and parts produced with additive manufacturing by laser powder bed fusion. The effect of heat treatment was also considered and the stage in which it was applied. The experiments showed very good weldability and the results were verified with microstructural analysis and tensile testing with digital image correlation equipment. Microstructures of the welds revealed morphology consisting of equiaxed and columnar grains in somewhat random orientation. Tensile tests showed that the 75% higher yield strength of the printed material compared to sheet metal leads to uneven elongation of the dissimilar joint and the part breaks from the sheet metal side. Hardness measurements showed higher values for the printed side (225 HV) compared to sheet metal side (170 HV). All the welded specimens broke outside of the welds showing a good weldability independent of the heat treatment stage.

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.

Adjusted Process Conditions in Laser Powder Bed Fusion to Obtain a Single-Crystal-Like Microstructure in IN718

2021 ◽  
Vol 1161 ◽  
pp. 39-46
Author(s):  
Alexander F. Frey ◽  
Christoph Seyfert ◽  
Peter J. Holfelder
Keyword(s):  
Mechanical Properties ◽  
Single Crystal ◽  
Base Alloy ◽  
Spot Size ◽  
Process Conditions ◽  
Powder Bed Fusion ◽  
Laser Powder Bed Fusion ◽  
Powder Bed ◽  
Anisotropic Mechanical Properties ◽  
Nickel Base

The nickel base alloy IN718 was manufactured by Laser Powder Bed Fusion (LPBF) using a laser spot size of 1024 μm and a laser power of 1.3 kW at a layer thickness of 160μm. The resulting porosity, microstructure and mechanical properties are presented. Very coarse and in build direction elongated grains are stacked to form a polycrystalline material with sharp single-crystal-like texture. The appearance of ∑5 grain boundaries between coincidence side lattices is recognized. Tensile testing shows highly anisotropic mechanical properties according to the revealed texture. Increasing the hatch distance reduces the severity of the texture.

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