Evolution of microstructure and mechanical properties in 2205 duplex stainless steels during additive manufacturing and heat treatment

Nima Haghdadi, Carina Ledermueller, Hansheng Chen, Zibin Chen, Qian Liu, Xiaopeng Li, Gregory Rohrer, Xiaozhou Liao, Simon Ringer, Sophie Primig

Research output: Journal article publicationJournal articleAcademic researchpeer-review

10 Citations (Scopus)

Abstract

Metal additive manufacturing (AM) offers exceptional design freedom, but its high thermal gradients often generate non-equilibrium microstructures with chemical and interfacial instabilities. Steels that solidify as δ-ferrite often experience a further solid-state phase transformation to austenite during AM. The detailed nature of this phase transformation during AM is yet to be fully understood. Duplex stainless steel, which is known for its unique combination of high corrosion resistance and mechanical properties, is a suitable alloy to further study this phase transformation. The current study aims to gain novel insights into solid-state phase transformations and mechanical properties of duplex stainless steels during laser powder-bed fusion (LPBF). As-printed microstructures exhibit significant deviations when compared to conventionally manufactured counterparts in terms of phase balance and morphology, elemental partitioning, and interface character distribution. During LPBF, only a small fraction of austenite forms, mostly at the ferrite-ferrite grain boundaries, via a phase transformation accompanied by diffusion of interstitials. Austenite/ferrite boundaries are shown to terminate on {100}F//{111}A planes. This is due to the character of parent ferrite-ferrite boundaries which is dictated by the sharp <100> texture and geometry of austenite grains induced by directional solidification and epitaxial growth of ferrite. Benchmarking mechanical properties against a wrought counterpart demonstrates that AM offers high strength but relatively low ductility and impact toughness. A short heat treatment reverts the microstructure back to its equilibrium state resulting in balanced tensile and toughness properties, comparable to or even better than those of wrought counterparts.

Original languageEnglish
Article number142695
JournalMaterials Science and Engineering A
Volume835
DOIs
Publication statusPublished - 17 Feb 2022

Keywords

  • Additive manufacturing
  • Duplex stainless steel
  • Heat treatment
  • Mechanical properties
  • Microstructure

ASJC Scopus subject areas

  • Materials Science(all)
  • Condensed Matter Physics
  • Mechanics of Materials
  • Mechanical Engineering

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