Role of martensite decomposition in tensile properties of selective laser melted Ti-6Al-4V

Sheng Cao, Ruikun Chu, Xigen Zhou, Kun Yang, Qingbo Jia, Chao Voon Samuel Lim, Aijun Huang, Xinhua Wu

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55 Citations (Scopus)

Abstract

The as-Selective Laser Melted (as-SLMed) Ti-6Al-4V generally has a martensitic microstructure. In the present study, martensite decomposition was investigated in various annealed samples by XRD, SEM and TEM. It has been found that annealing at 700 °C or 800 °C for 2 h was not sufficient to obtain a fully decomposed microstructure. The amount of martensite did reduce greatly and volume fraction of β phase increased significantly when the annealing temperature increased from 700 to 800 °C. However, the best combination of mechanical property was not obtained. It is to be noted that annealing at 800 °C for 2 h is widely used for SLMed Ti-6Al-4V as reported in literature. Detailed SEM and TEM analysis revealed the presence of residual martensite containing twins and a high density of dislocations even in the 800 °C/2 h annealed sample. The twin was determined as {101¯1} <101¯2> type, which are retained twin formed in martensitic transformation during the cooling in SLM. Annealing at 800 °C for 6 h or more provided a fine equilibrium α + β microstructure, which provided a strong and ductile SLMed Ti-6Al-4V.

Original languageEnglish
Pages (from-to)357-363
Number of pages7
JournalJournal of Alloys and Compounds
Volume744
DOIs
Publication statusPublished - 5 May 2018

Keywords

  • Laser processing
  • Metals
  • Scanning and transmission electron microscopy
  • X-ray diffraction

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