Investigation of crystal growth mechanism during selective laser melting and mechanical property characterization of 316L stainless steel parts

Wang, Di; Song, Changhui; Yang, Yongqiang; Bai, Yuchao

doi:10.1016/j.matdes.2016.03.111

Cited by 476 publications

(164 citation statements)

References 30 publications

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“…of the cellular dendrites microstructure of 316 L steel manufactured by LPBF were consistent with previous reports [5][6][7][18][19][20][21][22]. XRD, EBSD, and TEM analysis carried out in the present investigation revealed a fully austenitic structure in the LPBF 316 L steel.…”

Section: Resultssupporting

confidence: 92%

Microstructure, Solidification Texture, and Thermal Stability of 316 L Stainless Steel Manufactured by Laser Powder Bed Fusion

Krakhmalev

Fredriksson

Svensson

et al. 2018

Metals

134

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This article overviews the scientific results of the microstructural features observed in 316 L stainless steel manufactured by the laser powder bed fusion (LPBF) method obtained by the authors, and discusses the results with respect to the recently published literature. Microscopic features of the LPBF microstructure, i.e., epitaxial nucleation, cellular structure, microsegregation, porosity, competitive colony growth, and solidification texture, were experimentally studied by scanning and transmission electron microscopy, diffraction methods, and atom probe tomography. The influence of laser power and laser scanning speed on the microstructure was discussed in the perspective of governing the microstructure by controlling the process parameters. It was shown that the three-dimensional (3D) zig-zag solidification texture observed in the LPBF 316 L was related to the laser scanning strategy. The thermal stability of the microstructure was investigated under isothermal annealing conditions. It was shown that the cells formed at solidification started to disappear at about 800 • C, and that this process leads to a substantial decrease in hardness. Colony boundaries, nevertheless, were quite stable, and no significant grain growth was observed after heat treatment at 1050 • C. The observed experimental results are discussed with respect to the fundamental knowledge of the solidification processes, and compared with the existing literature data.

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Section: Resultssupporting

confidence: 92%

Microstructure, Solidification Texture, and Thermal Stability of 316 L Stainless Steel Manufactured by Laser Powder Bed Fusion

Krakhmalev

Fredriksson

Svensson

et al. 2018

Metals

134

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show abstract

“…The microstructure of the 316L sample fabricated by selective laser melting is shown in Figure 5. It displays a fine cellular/dendritic structure, similar to most of the samples prepared by SLM during to the fast cooling rates observed during the process [14][15][16][17][18][19]. This also explains the microstructural differences between the SLM prepared and conventionally cast/powder metallurgical microstructures.…”

Section: Resultssupporting

confidence: 56%

Characterization of 316L Steel Cellular Dodecahedron Structures Produced by Selective Laser Melting

et al. 2016

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Abstract:The compression behavior of different 316L steel cellular dodecahedron structures with different density values were studied. The 316L steel structures produced using the selective laser melting process has four different geometries: single unit cells with and without the addition of base plates beneath and on top, and sandwich structures with multiple unit cells with different unit cell sizes. The relation between the relative compressive strength and the relative density was compared using different Gibson-Ashby models and with other published reports. The different aspects of the deformation and the mechanical properties were evaluated and the deformation at distinct loading levels was recorded. Finite element method (FEM) simulations were carried out with the defined structures and the mechanical testing results were compared. The calculated theory, simulation estimation, and the observed experimental results are in good agreement.

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“…The general claim is that HV values must not depend on the load. A publication of 2016 gives a value of 281.6 HV0.1 (N/mm 2 ) at 0.981 N load [11]. The rounding of the Vickers pyramid is not given (its influence is eliminated by comparison with test-plates impressions), but we calculate for ideal Vickers a depth of 3.66 µm.…”

Section: Vickers Hardness Test and Other One-point-load Macrohardnessmentioning

confidence: 99%

Challenge of Industrial High-load One-point Hardness and of Depth Sensing Modulus

Kaupp¹

2017

J Material Sci Eng

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The physics of industrial single-point force indentation hardness measurements (Vickers, Knoop, Brinell, Rockwell, Shore, Leeb, and others) is compared with the depth-sensing nano, micro, and macro instrumental hardness technique that provides several further mechanical parameters, when using the correct force/depth curves exponent 3/2 on the depth of the loading curves. Only the latter reveal phase change onset with transition energy, and temperaturedependent activation energy, which provides important information for applications of all types of solids, but is not considered in the ISO or ASTM standards. Furthermore, the high-load one-point techniques leave the inevitably even stronger and more diverse consecutive phase-transformations undetected, so that the properties of pristine materials are not obtained. But materials are mostly not (continuously) applied under so high load, which must lead to severe misinterpretations. The dilemma of ISO or ASTM standards violating the basic energy law, the dimensional law, and denying the occurrence of phase changes under load is demonstrated with the physics of depth-sensing indentations. Transformation of iterated ISO-hardness and finite element simulated hardness to physical hardness is exemplified. The one-point techniques remain important for industry, but they must be complemented by physical hardness with detection of the phase transformation onset sequences for the reliability of their results.The elastic modulus E ISO from unloading curves as hitherto unduly called "Young's" modulus has nothing in common with unidirectional Young's modulus according to Hook's law, because the skew tip faces collect contributions from all crystal faces including shear moduli, while iteration fit is to Young's modulus of a standard. Unphysical and also physically corrected multidirectional indentation moduli mixtures of mostly anisotropic materials and there from deduced mechanical parameters have no physical basis and none of these should be used any more. A possible solution of this dilemma might be the use of indentation-E phys and bulk moduli K from hydrostatic compression measurements. The reasons for obeying physical laws in the mechanics of materials are stressed.

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Investigation of crystal growth mechanism during selective laser melting and mechanical property characterization of 316L stainless steel parts

Cited by 476 publications

References 30 publications

Microstructure, Solidification Texture, and Thermal Stability of 316 L Stainless Steel Manufactured by Laser Powder Bed Fusion

Microstructure, Solidification Texture, and Thermal Stability of 316 L Stainless Steel Manufactured by Laser Powder Bed Fusion

Characterization of 316L Steel Cellular Dodecahedron Structures Produced by Selective Laser Melting

Challenge of Industrial High-load One-point Hardness and of Depth Sensing Modulus

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