Effect of cooling rate on microstructure and fracture characteristics of β-rich α + β type Ti-4.5Al-3V-2Mo-2Fe alloy

Gunawarman, M. Niinomi, K. Fukunaga, D. Eylon, S. Fujishiro, C. Ouchi

Research output: Contribution to journalArticle

18 Citations (Scopus)

Abstract

This study investigated the effect of cooling rate on microstructure and fracture characteristics of β-rich α + β type Ti-4.5Al-3V-2Mo-2Fe alloy rolled plate. Particular attention was paid to the roles of the local and continuous secondary phases within prior β grain in the static fracture toughness. A variety of microstructures containing different types, morphologies, sizes and volume fractions of secondary phases were obtained in matrix β (within prior β grain) with varying cooling rates; namely, water-quenching (WQ), air-cooling (AC), furnace-cooling and slow furnace-cooling (SFC) from various solutionizing temperatures in the α + β field. The types of secondary phases are martensite α (orthorhombic α″), acicular α and plate-like α observed in WQ, AC and FC specimens, respectively. While, there is no or lack secondary phase observed in matrix β for SFC specimen. Deformation-induced martensite (α″), DIM, was observed in WQ specimens after testing. The results showed that the fracture toughness, JIC, and calculated flow stress, σf, of the microstructures containing a secondary phase depend mainly on the type and width of the secondary phase. The JIC of microstructures containing a secondary phase, in general, is superior to that of the microstructures lacking secondary phases. Both the martensite α and DIM appear to increase JIC. In a particular condition, JIC decreases slightly with increasing width of acicular α for microstructure containing predominantly local acicular α, but increases monotonously further increases in the width of acicular α. JIC increases considerably with increasing width of plate-like α. The increase of JIC is mainly due to increasing the effect of extrinsic toughening mechanism.

Original languageEnglish
Pages (from-to)1339-1348
Number of pages10
JournalMaterials Transactions
Volume42
Issue number7
DOIs
Publication statusPublished - 2001 Jan 1

Keywords

  • Fracture characteristics
  • Fracture toughness
  • Microstructure
  • Secondary phase
  • Ti-4.5Al-3V-2Mo-2Fe
  • β-rich α + β titanium alloy

ASJC Scopus subject areas

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

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