Recrystallization-based grain boundary engineering of 316L stainless steel produced via selective laser melting

Gao, Shubo; Hu, Zhiheng; Duchamp, Martial; Krishnan, P. S. Sankara Rama; Tekumalla, Sravya; Song, Xu; Seita, Matteo

doi:10.1016/j.actamat.2020.09.015

Cited by 167 publications

(40 citation statements)

References 63 publications

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“…The discussion of the sluggish recrystallization is available in the appended manuscript IV, where the solid microstructural evidence and careful mathematic validation are included. Interestingly, a recently published paper [89] on LPBF 316L stainless steel found that the grain boundary migration is less influenced in the sparser solute-segregation network region, which supports the interdendritic trapping effect on the recrystallization process.…”

Section: Sluggish Recrystallizationmentioning

confidence: 80%

Alloy Design and Characterization of γ′ Strengthened Nickel-based Superalloys for Additive Manufacturing

2021

Linköping Studies in Science and Technology. Licentiate Thesis

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Nickel-based superalloys, an alloy system bases on nickel as the matrix element with the addition of up to 10 more alloying elements including chromium, aluminum, cobalt, tungsten, molybdenum, titanium, and so on. Through the development and improvement of nickel-based superalloys in the past century, they are well proved to show excellent performance at the elevated service temperature. Owing to the combination of extraordinary high-temperature mechanical properties, such as monotonic and cyclic deformation resistance, fatigue crack propagation resistance; and high-temperature chemical properties, such as corrosion and oxidation resistance, phase stability, nickel-based superalloys are widely used in the critical hot-section components in aerospace and energy generation industries. The success of nickel-based superalloy systems attributes to both the well-tailored microstructures with the assistance of carefully doped alloying elements, and the intently developed manufacturing processes. The microstructure of the modern nickel-based superalloys consists of a two-phase configuration: the intermetallic precipitates (Ni,Co)3(Al,Ti,Ta) known as γ′ phase dispersed into the austenite γ matrix, which is firstly introduced in the 1940s. The recently developed additive manufacturing (AM) techniques, acting as the disruptive manufacturing process, offers a new avenue for producing the nickel-based superalloy components with complicated geometries. However, γ′ strengthened nickel-based superalloys always suffer from the micro-cracking during the AM process, which is barely eliminated by the process optimization. On this basis, the new compositions of γ′ strengthened nickel-based superalloy adapted to the AM process are of great interest and significance. This study sought to design novel γ′ strengthened nickel-based superalloys readily for AM process with limited cracking susceptibility, based on the understanding of the cracking mechanisms. A two-parameter model is developed to predict the additive manufacturability for any given composition of a nickel-based superalloy. One materials index is derived from the comparison of the deformation-resistant capacity between dendritic and interdendritic regions, while another index is derived from the difference of heat resistant capacity of these two spaces. By plotting the additive manufacturability diagram, the superalloys family can be categorized into the easy-to-weld, fairly-weldable, and non-weldable regime with the good agreement of the existed knowledge. To design a novel superalloy, a Cr-Co-MoW -Al-Ti-Ta-Nb-Fe-Ni alloy family is proposed containing 921,600 composition recipes in total. Through the examination of additive manufacturability, undesired phase formation propensity, and the precipitation fraction, one composition of superalloy, MAD542, out of the 921,600 candidates is selected. Validation of additive manufacturability of MAD542 is carried out by laser powder bed fusion (LPBF). By optimizing the LPBF process parameters, the crack-free MAD542 part is achieved. I...

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Section: Sluggish Recrystallizationmentioning

confidence: 80%

Alloy Design and Characterization of γ′ Strengthened Nickel-based Superalloys for Additive Manufacturing

2021

Linköping Studies in Science and Technology. Licentiate Thesis

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“…Based on the qualitative analysis of the KAM image, the SLM-prepared 316L SS exhibited high residual stress, which results from multiple thermal cycles and especially thermal shrinkage stress during rapid melting and solidification. To convert local misorientation into the density of geometrically necessary dislocation (GND), the following formula is used:

where

is the GND density at points, θ denotes the local misorientation angle ( Gao et al, 2020 ), b represents the Burger’s vector (0.25 nm), and u is the scan step (3 μm) of EBSD. The average

of the 0°, 45°, 60°, and 90° samples were 3.89 × 10 15 m −2 , 4.26 × 10 15 m −2 , 4.29 × 10 15 m −2 , and 4.56 × 10 15 m −2 , respectively.…”

Section: Resultsmentioning

confidence: 99%

“…Additive manufacturing (AM) has great development prospects in the medical, automotive, aerospace, and mold industries and is currently a global manufacturing trend, as stated by Song S. et al (2020). Selective laser melting (SLM), as one of the AM technology, "prints" materials and components directly from a computer-aided design file, thereby offering unique advantages of design freedom for complex parts without the need for molds (Shu et al, 2020).…”

Section: Introductionmentioning

confidence: 99%

Study on Mechanism of Structure Angle on Microstructure and Properties of SLM-Fabricated 316L Stainless Steel

et al. 2021

Front. Bioeng. Biotechnol.

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In this study, seven 316L stainless steel (316L SS) bulks with different angles (0°, 15°, 30°, 45°, 60°, 75°, and 90°) relative to a build substrate were built via selective laser melting (SLM). The influences of different angles on the metallography, microstructure evolution, tensile properties, and corrosion resistance of 316L SS were studied. The 0° sample showed the morphology of corrugated columnar grains, while the 90° sample exhibited equiaxed grains but with a strong <101> texture. The 60° sample had a good strength and plasticity: the tensile strength with 708 MPa, the yield strength with 588 MPa, and the elongation with 54.51%. The dislocation strengthening and grain refinement play a vital role in the mechanical properties for different anisotropy of the SLM-fabricated 316L SS. The 90° sample had greater toughness and corrosion resistance, owing to the higher volume fraction of low-angle grain boundaries and finer grains.

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“…The diameter of the spherical powder used by the LPBF system is commonly in the range of 10–60 μm [ 27 ], and the layer of 20–60 μm thickness is frequently chosen. Recently, the micro LPBF has been proposed and reported [ 28 , 29 , 30 ], which possesses finer microstructure [ 28 , 29 , 30 ] and smaller distortion [ 28 , 29 , 31 ] than conventional ones. Therefore, a micro LPBF system based on Han’s laser machine frame M100 with 25 μm laser beam, 10 μm slice layer and 5–25 μm powder is employed to achieve a finer structure in this work, which is beneficial to the fabrication of TWS.…”

Section: Introductionmentioning

confidence: 99%

Achieving Triply Periodic Minimal Surface Thin-Walled Structures by Micro Laser Powder Bed Fusion Process

Ding

Song

2021

Micromachines

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Recently, triply periodic minimal surface (TPMS) lattice structures have been increasingly employed in many applications, such as lightweighting and heat transfer, and they are enabled by the maturation of additive manufacturing technology, i.e., laser powder bed fusion (LPBF). When the shell-based TPMS structure’s thickness decreases, higher porosity and a larger surface-to-volume ratio can be achieved, which results in an improvement in the properties of the lattice structures. Micro LPBF, which combines finer laser beam, smaller powder, and thinner powder layer, is employed in this work to fabricate the thin-walled structures (TWS) of TPMS lattice by stainless steel 316 L (SS316L). Utilizing this system, the optimal parameters for printing TPMS-TWS are explored in terms of densification, smoothness, limitation of thickness, and dimensional accuracy. Cube samples with 99.7% relative density and a roughness value of 2.1 μm are printed by using the energy density of 100 J/mm3. Moreover, a thin (100 μm thickness) wall structure can be fabricated through optimizing parameters. Finally, the TWS samples with various TPMS structures are manufactured to compare their heat dissipation capability. As a result, TWS sample of TPMS lattice exhibits a larger temperature gradient in the vertical direction compared to the benchmark sample. The steady-state temperature of the sample base presents a 7 K decrease via introducing TWS.

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Recrystallization-based grain boundary engineering of 316L stainless steel produced via selective laser melting

Cited by 167 publications

References 63 publications

Alloy Design and Characterization of γ′ Strengthened Nickel-based Superalloys for Additive Manufacturing

Alloy Design and Characterization of γ′ Strengthened Nickel-based Superalloys for Additive Manufacturing

Study on Mechanism of Structure Angle on Microstructure and Properties of SLM-Fabricated 316L Stainless Steel

Achieving Triply Periodic Minimal Surface Thin-Walled Structures by Micro Laser Powder Bed Fusion Process

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