Variations in the microstructure and hardness with solution treating and aging conditions in new α+β titanium alloy Ti-4.5%Al-6%Nb-2%Fe-2%Mo

Takahiro Hirano, Taichi Murakami, Takayuki Narushima, Chiaki Ouchi

Research output: Contribution to journalArticlepeer-review

2 Citations (Scopus)

Abstract

Variations in the microstructure and hardness with solution treating and aging conditions in new α+β titanium alloy Ti-4.5%Al-6%Nb-2%Fe-2%Mo were investigated. Solution treating (ST) temperatures were varied from 1 048 to 1 173 K with both cooling conditions of water quenching and air cooling. Cooling rate after solution treating was varied from 1 to 60 K/s using a hot working simulator. Age-hardening was investigated at temperatures ranged from 573 to 823 K and aging time periods were varied in the range from 0.36 to 32.4 ks. An extremely fine two-phase microstructure with α grain size of around 1 μm was obtained at ST temperature of 1 048 K. The large amount of retained β phase was obtained by solution treating at temperatures below 1 098 K, and the amounts of α″ martenslte and athermal ω phase increased with an elevation of ST temperature above 1 098 K. For solution treating with water quenching, no hardness variation with solution treating temperature was observed. Age-hardening at the temperatures above 723 K took place at an extremely short aging time. Peak-age was observed in such a short aging time period as 0.36 ks, and hardness value at peak-age increased markedly and continuously with an elevation of solution treating temperature. Age-hardening was confirmed to be caused by very fine a precipitates, and age-hardening behavior noted above was explained by athermal ω phase playing a role of a nucleus for a precipitate.

Original languageEnglish
Pages (from-to)1042-1049
Number of pages8
JournalIsij International
Volume47
Issue number7
DOIs
Publication statusPublished - 2007

Keywords

  • Age-hardening
  • Athermal ω
  • Retained β phase
  • Solution treating
  • Transformed products
  • Two-phase microstructure
  • α+β titanium alloy

ASJC Scopus subject areas

  • Mechanics of Materials
  • Mechanical Engineering
  • Metals and Alloys
  • Materials Chemistry

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