Structural evolution during nanostructuring of additive manufactured 316L stainless steel by high-pressure torsion

Han, Jae-Kyung; Liu, Xiaojing; Lee, Isshu; Kuzminova, Yulia O.; Evlashin, Stanislav A.; Liß, Klaus-Dieter; Kawasaki, Megumi

doi:10.1016/j.matlet.2021.130364

Cited by 16 publications

(8 citation statements)

References 10 publications

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“…Figure shows the XRD profile for the AM 316L SS in as‐built and after HPT up to 8 [ 23 ] and 15 turns. The XRD peaks measured over the disk surfaces show a series of f.c.c.…”

Section: Resultsmentioning

confidence: 99%

“…Although fast cooling lost capability in evaluating the peak shifts from 1200 K towards 850 K in the sample after HPT, reasonably consistent linear relationships are observed between thermal lattice expansion and contraction upon heating and cooling, respectively, in both sample conditions. XRD profile for the AM 316L SS in as-build and after HPT through 8 [23] and 15 turns under 6.0 GPa. (Adapted with permission.…”

Section: In Situ Heating Neutron Diffraction Measurementsmentioning

confidence: 99%

“…Thus, it is a great opportunity for applying the HPT technique to the AM metals, while their heating behavior and thermal stability yet have to be investigated for understanding the significance of nanostructuring to the AM metals. There are a limited number of reports to date on processing of nanostructured AM 316L grade steels by HPT for examining the structural changes, [ 23 ] microstructural changes, [ 24 ] and improved strengths, [ 25 ] but these HPT‐processed AM steels showed inconsistent martensitic transformation. A recent study using an HPT‐processed AM CoCrFeNi high‐entropy alloy demonstrated the improved strain hardenability in comparison with the conventionally manufactured cast counterpart after HPT.…”

Section: Introductionmentioning

confidence: 99%

“…Moreover, the pattern shows the presence of a primarily γ-austenite phase with a face-centered cubic ( f.c.c.) structure and a limited secondary phase of ε-martensite with a hexagonal close-packed (h.c.p) structure.Figure4shows the XRD profile for the AM 316L SS in as-built and after HPT up to 8[23] and 15 turns. The XRD peaks measured over the disk surfaces show a series of f.c.c.…”

mentioning

confidence: 99%

“…Figure 4. XRD profile for the AM 316L SS in as-build and after HPT through 8[23] and 15 turns under 6.0 GPa. (Adapted with permission [23].…”

mentioning

confidence: 99%

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In Situ Heating Neutron and X‐Ray Diffraction Analyses for Revealing Structural Evolution during Postprinting Treatments of Additive‐Manufactured 316L Stainless Steel

et al. 2021

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Herein, lab‐scale X‐ray diffraction and in situ heating neutron diffraction analyses for evaluating the structural changes at postprinting nanostructuring and structural relaxation upon heating, respectively, in an additive‐manufactured (AM) 316L stainless steel are conducted. The nanostructured AM steel after nanostructuring by high‐pressure torsion reached crystallite sizes of 23–26 nm, a dislocation density of ≈45 × 1014 m−2 and a microstrain of >0.008. A limited amount of deformation‐induced ε‐martensite was observed at a local region in the nanostructured AM steel. The time‐resolved neutron diffraction experiment upon heating successfully visualizes the sequential structural relaxation and linear thermal lattice expansion in the nanostructured AM steel. In practice, by calculating the changes in crystallite sizes, microstrains, and dislocation densities, the relaxation behaviors of the nanocrystalline AM steel is observed: 1) recovery with slow stress relaxation with increasing hardness up to 873 K, 2) recrystallization with accelerated stress relaxation at 873–973 K; and 3) grain growth above 973 K with (iii′) total stress relaxation in lattices up to 1023 K. In addition, this manuscript makes connections between the critical subjects in materials science of advanced manufacturing, metal processing and properties, and novel time‐resolved characterization techniques.

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“…Figure shows the XRD profile for the AM 316L SS in as‐built and after HPT up to 8 [ 23 ] and 15 turns. The XRD peaks measured over the disk surfaces show a series of f.c.c.…”

Section: Resultsmentioning

confidence: 99%

Section: In Situ Heating Neutron Diffraction Measurementsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

mentioning

confidence: 99%

“…Figure 4. XRD profile for the AM 316L SS in as-build and after HPT through 8[23] and 15 turns under 6.0 GPa. (Adapted with permission [23].…”

mentioning

confidence: 99%

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In Situ Heating Neutron and X‐Ray Diffraction Analyses for Revealing Structural Evolution during Postprinting Treatments of Additive‐Manufactured 316L Stainless Steel

et al. 2021

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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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X-ray line profile analysis study on the evolution of the microstructure in additively manufactured 316L steel during severe plastic deformation

Gubicza,

Kawasaki,

Dankházi

et al. 2023

J Mater Sci

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Abstract316L stainless steel was manufactured by additive manufacturing (AM), and then, the samples were severely deformed by the high-pressure torsion (HPT) technique. The evolution of the microstructure was monitored by X-ray line profile analysis. This method gives the crystallite size and the density of lattice defects, such as dislocations and twin faults. The AM-processing of the HPT disks was performed in two different modes: the laser beam was parallel or orthogonal to the normal direction of the disks. The subsequent HPT deformation was carried out for ½, 1, 5 and 10 turns. The microstructure and hardness evolution during HPT were similar regardless of the laser beam direction. For both sample series, the minimum achievable crystallite size was about 30 nm, while the dislocation density and the twin fault probability got saturated at the values of 300–350 × 1014 m−2 and 3.5–4%, respectively. The microstructure evolution during HPT of the AM-prepared 316L steel was compared with the HPT-induced changes in an as-cast counterpart. It was found that while the AM-prepared 316L steel remained a single-phase face-centered cubic γ-structure during HPT, in the as-cast samples a body-centered cubic (bcc) martensitic α-phase became the main phase with increasing the imposed strain of HPT due to the lower Ni content. In the saturation state achieved by HPT the initially as-cast 316L steel had a considerably higher hardness (about 6000 MPa) than that for the AM-prepared samples (~ 5000 MPa) due to the large fraction of the hard bcc phase formed during HPT.

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Structural evolution during nanostructuring of additive manufactured 316L stainless steel by high-pressure torsion

Cited by 16 publications

References 10 publications

In Situ Heating Neutron and X‐Ray Diffraction Analyses for Revealing Structural Evolution during Postprinting Treatments of Additive‐Manufactured 316L Stainless Steel

In Situ Heating Neutron and X‐Ray Diffraction Analyses for Revealing Structural Evolution during Postprinting Treatments of Additive‐Manufactured 316L Stainless Steel

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

X-ray line profile analysis study on the evolution of the microstructure in additively manufactured 316L steel during severe plastic deformation

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