Microstructural control during direct laser deposition of a β-titanium alloy

Chunlei Qiu, G.a. Ravi, Moataz M. Attallah

Research output: Contribution to journalArticlepeer-review

47 Citations (Scopus)
255 Downloads (Pure)

Abstract

A concern associated with Direct Laser Deposition (DLD) is the difficulty in controlling microstructure due to rapid cooling rates after deposition, particularly in beta-Ti alloys. In these alloys, the beta-phase is likely to exist following DLD, instead of the desirable duplex alpha + beta microstructure that gives a good balance of properties. Thus, in this work, a parametric study was performed to assess the role of DLD parameters on porosity, build geometry, and microstructure in a beta-Ti alloy, Ti–5Al–5Mo–5V–3Cr (Ti5553). The builds were examined using optical microscopy, scanning electron microscopy, and X-ray diffraction. Microhardness measurements were performed to assess the degree of re-precipitation of alpha-phase following an in situ dwelling and laser annealing procedure. The study identified several processing conditions that enable deposition of samples with the desired geometry and low porosity level. The microstructure was dominated by beta-phase, except for the region near the substrate where a limited amount of alpha-precipitates was present due to reheating effect. Although the microstructure was a mixture of equiaxed and columnar beta-grains alongside infrequent fine alpha-precipitates, the builds showed fairly uniform microhardness in different regions. In situ dwelling and annealing did not cause an obvious change in porosity, but did promote the formation of alpha-precipitates.
Original languageEnglish
Pages (from-to)21-30
JournalMaterials & Design
Volume81
Early online date12 May 2015
DOIs
Publication statusPublished - 15 Sep 2015

Keywords

  • Direct Laser Deposition
  • Parametric study
  • Beta-titanium alloys
  • Build geometry
  • Microstructure
  • Microhardness

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