Design of near α-Ti alloys using δ-parameter

Haruki Masuyama, Tomoki Kuroda, Yoshiaki Toda, Tetsuya Matsunaga, Tsutomu Ito, Masayuki Shimojo, Yoko Yamabe-Mitarai

Research output: Contribution to journalArticlepeer-review


In this study, to obtain a high solid-solution strengthening effect, new Ti alloys with bimodal structures were designed using the δ-parameter, which represents the average atomic radius misfit of the constituent elements used in high-entropy alloys. The δ-parameter calculated by the alloy composition was used to estimate the average solid-solution strengthening of the alloys. In particular, to clarify the effect of Zr and Sn in Ti alloys, Ti alloys were designed with different amounts of Zr and/or Sn using the δ-parameter. The compressive strength and creep behavior of the designed alloys were investigated to determine whether the δ-parameter is useful for designing strengthened alloys. The compressive strength of the designed alloys was comparable to or higher than that of the commercial TIMETAL834 alloy up to 650 °C. This indicates that the δ-parameter is a useful parameter for estimating the average solid-solution strengthening of the alloys. The compressive strengths of the designed alloys were approximately proportional to the 4/3 power of the δ−parameter. An increase in the strength by precipitation strengthening by α2-Ti3Al was also observed in the Sn-added alloys, whereas Ti3Al was not formed in the Sn-free alloys. Microstructural factors, such as the volume fraction of the equiaxed α phase and lamellar spacing in the bimodal microstructure, significantly contributed to the minimum creep strain rate, in addition to solid-solution and precipitation strengthening.

Original languageEnglish
Article number141589
JournalMaterials Science & Engineering A: Structural Materials: Properties, Microstructure and Processing
Publication statusPublished - 2021 Jul 21


  • Bimodal structure
  • Compression test
  • Creep
  • Solid-solution strengthening
  • Titanium alloy
  • δ−parameter

ASJC Scopus subject areas

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


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