Influence of High-Pressure Torsion on the Microstructure and Microhardness of Additively Manufactured 316L Stainless Steel
Influence of High-Pressure Torsion on the Microstructure and Microhardness of Additively Manufactured 316L Stainless Steel
High-pressure torsion (HPT) is known as an effective severe plastic deformation (SPD) technique to produce bulk ultrafine-grained (UFG) metals and alloys by the application of combined compressive force and torsional shear strains on thin disk samples. In this study, the microstructures and microhardness evolution of an additively manufactured (AM) 316L stainless steel (316L SS) processed through 5 HPT revolutions are evaluated at the central disk area, where the effective shear strains are relatively low compared to the peripheral regions. Scanning electron microscopy (SEM) analysis showed that the cellular network sub-structures in AM 316L SS were destroyed after 5 HPT revolutions. Transmission electron microscopy (TEM) observations revealed non-equilibrium ultrafine grained (UFG) microstructures (average grain size: ~115 nm) after 5 revolutions. Furthermore, energy dispersive x-ray spectroscopy (EDX) analysis suggested that spherical Cr-based nano-silicates are also found in the as-received condition, which are retained even after HPT processing. Vickers microhardness (HV) measurements indicated significant increase in average hardness values from ~220 HV before HPT processing to ~560 HV after 5 revolutions. Quantitative X-ray diffraction (XRD) patterns exhibit a considerable increase in dislocation density from ~0.7 × 1013 m−2 to ~1.04 × 1015 m−2. The super-high average hardness increment after 5 HPT revolutions is predicted to be attributed to the UFG grain refinement, significant increase in dislocation densities and the presence of the Cr-based nano-silicates, according to the model established based on the linear additive theory.
high-pressure torsion; laser powder bed fusion; severe plastic deformation; additive manufacturing; microstructure; microhardness
1-12
Mohd Yusuf, Shahir
5888c057-33da-45f3-a84d-95a291db8f34
Chen, Ying
d50ad788-57a8-4ab9-b4ea-f98e2aa617af
Gao, Nong
9c1370f7-f4a9-4109-8a3a-4089b3baec21
October 2021
Mohd Yusuf, Shahir
5888c057-33da-45f3-a84d-95a291db8f34
Chen, Ying
d50ad788-57a8-4ab9-b4ea-f98e2aa617af
Gao, Nong
9c1370f7-f4a9-4109-8a3a-4089b3baec21
Mohd Yusuf, Shahir, Chen, Ying and Gao, Nong
(2021)
Influence of High-Pressure Torsion on the Microstructure and Microhardness of Additively Manufactured 316L Stainless Steel.
Metals, 11 (10), , [1553].
(doi:10.3390/met11101553).
Abstract
High-pressure torsion (HPT) is known as an effective severe plastic deformation (SPD) technique to produce bulk ultrafine-grained (UFG) metals and alloys by the application of combined compressive force and torsional shear strains on thin disk samples. In this study, the microstructures and microhardness evolution of an additively manufactured (AM) 316L stainless steel (316L SS) processed through 5 HPT revolutions are evaluated at the central disk area, where the effective shear strains are relatively low compared to the peripheral regions. Scanning electron microscopy (SEM) analysis showed that the cellular network sub-structures in AM 316L SS were destroyed after 5 HPT revolutions. Transmission electron microscopy (TEM) observations revealed non-equilibrium ultrafine grained (UFG) microstructures (average grain size: ~115 nm) after 5 revolutions. Furthermore, energy dispersive x-ray spectroscopy (EDX) analysis suggested that spherical Cr-based nano-silicates are also found in the as-received condition, which are retained even after HPT processing. Vickers microhardness (HV) measurements indicated significant increase in average hardness values from ~220 HV before HPT processing to ~560 HV after 5 revolutions. Quantitative X-ray diffraction (XRD) patterns exhibit a considerable increase in dislocation density from ~0.7 × 1013 m−2 to ~1.04 × 1015 m−2. The super-high average hardness increment after 5 HPT revolutions is predicted to be attributed to the UFG grain refinement, significant increase in dislocation densities and the presence of the Cr-based nano-silicates, according to the model established based on the linear additive theory.
Text
Manuscript for Metal Special Issue-NG 21y1123
- Accepted Manuscript
More information
Accepted/In Press date: 27 September 2021
Published date: October 2021
Additional Information:
Funding Information:
S.M.Y. thanks the Faculty of Engineering and Physical Sciences, University of Southampton for their financial support. The TEM experiments were carried out by Y.C. with financial aids from the National Science Foundation of Fujian Province, China (No. 51601162) and High-Level Talent Funding for Xiamen Oversea Returnee.
Publisher Copyright:
© 2021 by the authors. Licensee MDPI, Basel, Switzerland.
Keywords:
high-pressure torsion; laser powder bed fusion; severe plastic deformation; additive manufacturing; microstructure; microhardness
Identifiers
Local EPrints ID: 452683
URI: http://eprints.soton.ac.uk/id/eprint/452683
ISSN: 2075-4701
PURE UUID: 2e39f557-f39e-4917-9d82-cd632a551a6d
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Date deposited: 11 Dec 2021 11:36
Last modified: 17 Mar 2024 02:53
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Author:
Ying Chen
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