New insights on cellular structures strengthening mechanisms and thermal stability of an austenitic stainless steel fabricated by laser powder-bed-fusion

Voisin, Thomas; Forien, Jean‐Baptiste; Perron, Aurélien; Aubry, Sylvie; Bertin, Nicolas; Samanta, Amit; Baker, Alexander A.; Wang, Y. Morris

doi:10.1016/j.actamat.2020.11.018

Cited by 310 publications

(94 citation statements)

References 65 publications

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“…Therefore, the borders between adjacent cells should not be interpreted as additional large-angle grain boundaries. Still, the borders between the cells are characterized by a high dislocation density, as transmission electron microscopy investigations made by Voisin et al and others showed [ 8 , 27 , 29 ]. The formation of the cellular substructure is based on the rapid solidification rate resulting from the typical small melt pools generated during the PBF-LB/M process.…”

Section: Resultsmentioning

confidence: 99%

Impact of the Allowed Compositional Range of Additively Manufactured 316L Stainless Steel on Processability and Material Properties

et al. 2021

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This work aims to show the impact of the allowed chemical composition range of AISI 316L stainless steel on its processability in additive manufacturing and on the resulting part properties. ASTM A276 allows the chromium and nickel contents in 316L stainless steel to be set between 16 and 18 mass%, respectively, 10 and 14 mass%. Nevertheless, the allowed compositional range impacts the microstructure formation in additive manufacturing and thus the properties of the manufactured components. Therefore, this influence is analyzed using three different starting powders. Two starting powders are laboratory alloys, one containing the maximum allowed chromium content and the other one containing the maximum nickel content. The third material is a commercial powder with the chemical composition set in the middle ground of the allowed compositional range. The materials were processed by laser-based powder bed fusion (PBF-LB/M). The powder characteristics, the microstructure and defect formation, the corrosion resistance, and the mechanical properties were investigated as a function of the chemical composition of the powders used. As a main result, solid-state cracking could be observed in samples additively manufactured from the starting powder containing the maximum nickel content. This is related to a fully austenitic solidification, which occurs because of the low chromium to nickel equivalent ratio. These cracks reduce the corrosion resistance as well as the elongation at fracture of the additively manufactured material that possesses a low chromium to nickel equivalent ratio of 1.0. A limitation of the nickel equivalent of the 316L type steel is suggested for PBF-LB/M production. Based on the knowledge obtained, a more detailed specification of the chemical composition of the type 316L stainless steel is recommended so that this steel can be PBF-LB/M processed to defect-free components with the desired mechanical and chemical properties.

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Section: Resultsmentioning

confidence: 99%

Impact of the Allowed Compositional Range of Additively Manufactured 316L Stainless Steel on Processability and Material Properties

et al. 2021

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“…3-3. Previous studies have shown that the microstructure of AM 316L SS is stable below 600°C [19][20][21][22][23][24][25][26][27][28].…”

Section: Microstructure Of Heat-treated Rod Specimensmentioning

confidence: 96%

“…The initial columnar grains started to lose their shapes, implying the occurrence of recrystallization. Voisin et al [22] found that the overall grain structures of AM 316L SS remained stable up to 800-1000°C and near defect-free grains formed at 1100°C. Deng et al [20] reported full recrystallization of AM 316L SS after annealing at 1065°C and 1150°C.…”

Section: Microstructure Of Heat-treated Rod Specimensmentioning

confidence: 99%

“…columnar grains within melt pools, subgranular cellular structures, high density dislocations within cell walls, boundary elemental segregation, and oxide particles distributed both at boundaries and in the matrix [15][16][17][18]. Post-build heat treatments are performed to relieve residual stresses and to produce desired microstructure and improved mechanical properties [19][20][21][22][23][24][25][26][27][28].…”

Section: Introductionmentioning

confidence: 99%

“…Thermal annealing at high temperature can cause thermal instability of the microstructure of the as-built AM 316L SS. Several studies have shown that the hardness and room-temperature yield stress drop continuously with increasing annealing temperatures above 600°C, and this strength reduction has been primarily attributed to the coarsening of cell structures [20][21][22]27]. The variations of the as-built microstructure resulting from the variations in processing conditions, feedstock, or even printer types also complicate the understanding of the thermal stability of the microstructure of AM 316L SS.…”

Section: Introductionmentioning

confidence: 99%

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Location-Dependent Mechanical Property Evaluation on Additively Manufacture Materials

Chen

Zhang

et al. 2021

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This report summarizes research activities conducted at Argonne National Laboratory in support of the development, qualification and certification of additively manufactured (AM) metallic components to allow for innovative reactor design and licensing for the Transformational Challenge Reactor (TCR). Focus is on the evaluation of high temperature mechanical properties including creep and fatigue of 316L stainless steel manufactured by the laser powder bed fusion process. Creep behavior of AM 316L stainless steel was evaluated for rods printed by either or a combination of both lasers of the dual-laser system of a Concept Laser-M2 printer to examine the consistency across the build plate. Creep tests were conducted at temperatures of 550, 575, 600, and 650°C and stresses between 175 and 300 MPa using ASTM standard-sized specimens. The effect of heat treatments at different temperatures on creep properties of AM 316L SS was examined to understand the processing-microstructure-property relationship. Fatigue properties of AM 316L SS were investigated for two print geometries (rod and plate) and in two build orientations of printed plates. Locations of specimens in the build were carefully tracked such that the testing data can be directly related to location-specific in situ data to establish links between printing process, post-printing treatment, microstructure and mechanical properties. The work is to support the development of a digital platform informed approach to AM component qualification and certification for nuclear applications.

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In Situ Neutron Diffraction Investigating Microstructure and Texture Evolution upon Heating of Nanostructured CoCrFeNi High‐Entropy Alloy

et al. 2023

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Herein, in situ temperature‐dependent neutron experiments investigate the microstructural evolution of additively and conventionally manufactured CoCrFeNi high‐entropy alloys, as‐received, and after grain refinement through high‐pressure torsion. The evolution of texture after grain refinement and during heating is consistent with typical fcc metals. Both conventional and modified Williamson–Hall analyses reveal that major contributions of microstresses stem from dislocations. For the nanostructured material, three temperature regimes are identified on a heating ramp, namely, stress recovery up to 800 K, followed by recrystallization at 850–960 K, and normal grain growth above, in line with the physical change of hardness increase on recovery, decrease on recrystallization, and cutback to the as‐manufactured values after grain growth. The as‐printed material exposes higher dislocation density than as‐cast, reducing slightly upon heating, while there is limited temperature dependence on the lower dislocation density of the as‐cast specimen. Stored energies have been elaborated for residual stress and Bauschinger contributions, dislocation energy, grain boundary amounts, and vacancy contents with scenarios of vacancy expulsion leading to recrystallization. Ultimately, the fully recrystallized nanostructured material shows the lowest dislocation density, which may render a recipe for stress release in additively manufactured materials.

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New insights on cellular structures strengthening mechanisms and thermal stability of an austenitic stainless steel fabricated by laser powder-bed-fusion

Cited by 310 publications

References 65 publications

Impact of the Allowed Compositional Range of Additively Manufactured 316L Stainless Steel on Processability and Material Properties

Impact of the Allowed Compositional Range of Additively Manufactured 316L Stainless Steel on Processability and Material Properties

Location-Dependent Mechanical Property Evaluation on Additively Manufacture Materials

In Situ Neutron Diffraction Investigating Microstructure and Texture Evolution upon Heating of Nanostructured CoCrFeNi High‐Entropy Alloy

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