Nano-twining and deformation-induced martensitic transformation in a duplex stainless steel 2205 fabricated by laser powder bed fusion
File(s)
Published version
Author(s)
Type
Journal Article
Abstract
Duplex stainless steels (DSSs) possess desirable combinations of mechanical properties and excellent corrosion resistance due to their composition and equilibrium microstructure of roughly equivalent fractions of ferrite and austenite. They are used in harsh environments such as marine infrastructures, oil & gas, and paper & pulp industries. Components with complex geometries are often required for these applications. Additive manufacturing (AM) techniques such as laser powder bed fusion (LPBF) can be harnessed to fabricate components with greatest complexity. However, AM fabrication is well-known to promote non-equilibrium microstructures with high dislocation densities and Cr2N precipitates, resulting in inferior ductility. This is generally regarded as a challenge, however, short heat treatments of such as-built microstructures have been shown to attain refined duplex equilibrium microstructures. Recently, annealed LPBF DSS 2205 has been reported to possess strength higher than wrought counterparts and ductility properties better than the as-built state. However, the microstructural phenomena and deformation mechanisms behind these attractive properties remain poorly understood. Through multi-scale microstructural characterization, we show that the improved strength results not only from the hard ferrite phase, but also fine austenite grain size and nanoscale oxide dispersion strengthening. The enhanced ductility may be attributed to a combination of deformation mechanisms including dislocation slip, stacking fault formation, deformation twinning, and a deformation-induced martensitic transformation. We discuss how the level of microstructural complexity and solid-state phase transformations during LPBF and annealing can unlock multiple strengthening mechanisms during tensile deformation. Such fundamental understanding is crucial for designing AM parts with reproducible and optimised mechanical properties.
Date Issued
2024-03-25
Date Acceptance
2024-04-02
Citation
Additive Manufacturing, 2024, 84
ISSN
2214-8604
Publisher
Elsevier BV
Journal / Book Title
Additive Manufacturing
Volume
84
Copyright Statement
© 2024 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).
License URL
Identifier
http://dx.doi.org/10.1016/j.addma.2024.104110
Publication Status
Published
Article Number
104110
Date Publish Online
2024-04-03