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Clarification of processes for ordering and precipitation of long-period superstructures in Al-rich TiAl rapidly solidified ribbons

Research Project

Project/Area Number 11650719
Research Category

Grant-in-Aid for Scientific Research (C)

Allocation TypeSingle-year Grants
Section一般
Research Field Structural/Functional materials
Research InstitutionOsaka University

Principal Investigator

NAKANO Takayoshi  Graduate School of Engineering, Osaka University Assistant Professor, 大学院・工学研究科, 講師 (30243182)

Project Period (FY) 1999 – 2000
Project Status Completed (Fiscal Year 2000)
Budget Amount *help
¥3,600,000 (Direct Cost: ¥3,600,000)
Fiscal Year 2000: ¥1,800,000 (Direct Cost: ¥1,800,000)
Fiscal Year 1999: ¥1,800,000 (Direct Cost: ¥1,800,000)
KeywordsLong-period superstructure / γ-TiAl alloy / Al_5Ti_3 structure / Al_2Ti structure / Electron diffraction / {310) concentration wave / Ordering process / Hardeness / L1_0母相 / TEM / XRD / 散漫散乱 / 遷移構造 / (310)濃度波 / Ga_3Ti_2構造 / Al_5Ti_3 / h-Al_2Ti / APB / 周期性 / 急冷凝固 / バリアント
Research Abstract

Some long-period superstructures based on the L1_0 structure are formed in the Al-rich TiAl region of γ-TiAl expected as high-temperature heat-resistance materials. Mechanical properties of the Al-rich TiAl alloys are controlled depending on periodic-structure, morphology and distribution of these superstructures. In this study, processes of ordering and precipitation were clarified in the (Al, Ga)-rich (Al, Ga) Ti region using rapidly solidified ribbons containing the superstructures with a low degree of order.
Firstly, it was found by the detailed TEM observation that stability of these superstructures formed in the Al-rich TiAl region depends strongly on annealing temperature and Al concentration. Profit annealing changes the structure and periodicity of stable superstuctures. The stable superstructure was, for example, changed from Al_5Ti_3 to r-Al_2Ti through h-Al_2Ti. The transformation process was understood on the basis of crystal symmetry and lattice misfit of superstructures.
T … More he next year, an investigated compositional area was expanded from the Ti-Al binary to the Ti-Al-Ga ternary region in order to clarify the ordering process and transitional superstructures. In the Ti-Ga binary system, the Ga_3Ti_2-type superstructure with 5-fold periodicity with respect to the L1_0 matrix exists, thus the phase stability was discussed among three superstructures with different periodic structures from 3 to 5 fold-periodicity. In the (Al, Ga)-rich (Al, Ga) Ti region, continuous solid-solution area of the L1_0 matrix phase exists and some superstructures with different periodicities appeared depending on annealing temperature and composition in this region. The stable phase changes from the 2 : 1 to 3 : 2 structure through the 5 : 3 structure with a decrease in Al concentration or annealing temperature. This transitional process was explained by an continuous change in {310) concentration waves.
The above results can resolve phase stability and transitional process of the superstructures closely related to the mechanical properties of γ-TiAl alloys. Less

Report

(3 results)
  • 2000 Annual Research Report   Final Research Report Summary
  • 1999 Annual Research Report
  • Research Products

    (5 results)

All Other

All Publications (5 results)

  • [Publications] T.Nakano et al.: "Ordering process of Al_5Ti_3, h-Al_2Ti and r-Al_2Ti with f.C.C-based Long-Period Superstructures in Rapidly Solidified Al-rich TiAl Alloys."Acta Materialia. 47. 1091-1104 (1999)

    • Description
      「研究成果報告書概要(和文)」より
    • Related Report
      2000 Final Research Report Summary
  • [Publications] T.Nakano et al.: "Effect of Al_2Ti Phase on Plastic Behavior in Ti-62.5 at.% Al Singlecrystals."M.R.S.Sympo.Pro.. 552. KK5.9.1-KK5.9.6 (1999)

    • Description
      「研究成果報告書概要(和文)」より
    • Related Report
      2000 Final Research Report Summary
  • [Publications] T.Nakano, A.Negishi, K.Hayashi and Y.Umakoshi: "Ordering Process of Al_5Ti_3, h-Al_<>Ti and r-Al_2Ti with f.c.c.-based Long-Period Superstructures in Rapidly Solidified Al-rich TiAl Alloys"Acta Materialia. 47[4]. 1091-1104 (1999)

    • Description
      「研究成果報告書概要(欧文)」より
    • Related Report
      2000 Final Research Report Summary
  • [Publications] T.Nakano, H.Hayashi, K.Ashida and Y.Umakoshi: "Effect of Al_2Ti Phase on Plastic Behavior in Ti-62.5at.%Al Single Crystals"M.R.S Sympo.Pro.. 552. KK5.9.1-6 (1999)

    • Description
      「研究成果報告書概要(欧文)」より
    • Related Report
      2000 Final Research Report Summary
  • [Publications] T.Nakano et al.: "Ordering process of Al_5Ti_3,h-Al_2Ti and r-Al_2Ti with F.C.C.-based long-period superstructures in rapidly solidified Al-rich TiAl alloys"Acta materialia. 47No.4. 1091-1104 (1999)

    • Related Report
      1999 Annual Research Report

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Published: 1999-04-01   Modified: 2016-04-21  

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