Formation of a transition V-rich structure during the α' to α + β phase transformation process in additively manufactured Ti-6Al-4V

Hao Wang, Qi Chao, Hansheng Chen, Zibin Chen (Corresponding Author), Sophie Primig, Wei Xu, Simon Ringer (Corresponding Author), Xiaozhou Liao (Corresponding Author)

Research output: Journal article publicationJournal articleAcademic researchpeer-review

Abstract

Ti-6Al-4V parts fabricated by laser powder-bed fusion (L-PBF) additive manufacturing often suffer from poor ductility and low toughness due to the predominance of the acicular α' martensitic phase in their microstructures. This challenge can be overcome by manipulation of the L-PBF thermal history to introduce an α'→ α+β decomposition, resulting in a fine lamellar α+β structure with a combination of excellent strength and ductility. Understanding the details of the α'→ α+β phase transformation process is critical for fabricating titanium alloys with excellent mechanical properties. Through a systematic electron microscopy characterisation of the microstructural evolution of a Ti-6Al-4V alloy fabricated by L-PBF, here we reveal that the α'→ α+β phase transformation occurs in two steps: α'→ α+ α HME (high in Mo eq) and α HME → β, in which α HME is a newly discovered non-equilibrium structure with a hexagonal close-packed structure and with a composition close to that of the β phase.

Original languageEnglish
Article number118104
JournalActa Materialia
Volume235
DOIs
Publication statusPublished - 15 Aug 2022

Keywords

  • Additive manufacturing
  • Laser powder-bed fusion
  • Ti alloys
  • Ti-6Al-4V

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Ceramics and Composites
  • Polymers and Plastics
  • Metals and Alloys

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