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1997 Fiscal Year Final Research Report Summary

Anomalous high-temperature strengthening in alpha Ti-Al solid-solution alloys

Research Project

Project/Area Number 07455252
Research Category

Grant-in-Aid for Scientific Research (B)

Allocation TypeSingle-year Grants
Section一般
Research Field Physical properties of metals
Research InstitutionTohoku University

Principal Investigator

KOIKE Jun-ichi  Tohoku University Graduate School of Engineering Associate Professor, 大学院・工学研究科, 助教授 (10261588)

Project Period (FY) 1995 – 1997
Keywordstitanium / alpha titanium / high-temperature strength / mechanical properties / shrot range order
Research Abstract

Tensile tests were performed in Ti- (7-13) at.%Al alloys. Temperature dependence and strain-rate dependence on deformation behavior were investigated. The possibility of the strength anomaly athigh temperatures was examined and its reason was discussed, based on the obtained results and the reported results for alloys with low Al concentrations.
In the case of low-aluminum alloys containing less than 5mol%Al, the stress-strain rate relationship showed transition of the stress exponent from 3.5 to 4.6. The concentration dependence of flow stress was found to agree with theroreticaly predicted behavior by an ordinarly solid-solution herdening theory. In the case of concentrated alloys containing more than 5%Al, no transition was observed and the stress exponent was found to be a constant value of 3.5. The concentration dependence of flow stress was more than twice as large as the theoretically predicted calues, indicating the anomalous high-temperature strengthening in concentrated alpha Ti-Al solid-solution alloys.
Structural analysis by X-day diffraction and transmission electron microscopy suggested the presence of a short-range ordered (SRO) structure. The possibility of the SRO formation was investigated by Monte Carlo calculation. It was found that the SRO structure became noticeable for a concetration of more than 5 mol%. The SRO tedency was also found to increase with increasing the aluminum concentration. Since the presence of the ordered structure increases flow stress, the anomalous strengthening in the Ti-Al alloy was found to be caused by the formation of the SRO structure.

  • Research Products

    (12 results)

All Other

All Publications (12 results)

  • [Publications] 小池 淳一: "High temperature deformation characteristics of sintered alumina having amorphous grain boundaries" Materials Science Forum. 233-234. 351-358 (1997)

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] 小池 淳一: "Evvects of grain boundary amorphous phase on high temperature ductility in alumina polycrystals" Materials Science and Engineering A. A234-236. 529-532 (1997)

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] 小池 淳一: "Influence of liquid-phase inclusion onhigh-temperature deformation behavior in A1-Bi alloys" Materials Science and Engineering A. A234-236. 525-528 (1997)

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] 小池 淳一: "Microstructure and superplasticity in A1-Mg alloy composites reinforced with siliconnitride particles" Materials Science Forum. 243-245. 277-285 (1997)

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] 小池 淳一: "Effects of the liquid phase on the high-tempearture tensile ductility:From embrittlement to superplasticity" Philosophical Magazine A. (印刷中). (1998)

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] 小池 淳一: "Thermal cycling fatigue and deformation mechanism in aluminum alloy thin films on silicon" Journal of Materials Research. (印刷中). (1998)

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] Junichi Koike: "High temperature deformation characteristics of sintered alumina having amorphous grain boundaries" Materials Science Forum. 233-234. 351-358 (1997)

    • Description
      「研究成果報告書概要(欧文)」より
  • [Publications] Junichi Koike: "Effects of grain boundary amorphous phase on high temperature ductility in alumina polycrystals" Materials Science and Engineering. A,A234-236. 529-532 (1997)

    • Description
      「研究成果報告書概要(欧文)」より
  • [Publications] Junichi Koike: "Influence of liquid-phase inclusion on high temperature deformation behavior in Al-Bi alloys" Materials Science and Engineering. A,A234-236. 525-528 (1997)

    • Description
      「研究成果報告書概要(欧文)」より
  • [Publications] Junichi Koike: "Microstructure and superplasticity in Al-Mg alloy composites reinforced with silicon nitride particles" Materials Science Forum. 243-245. 277-285 (1997)

    • Description
      「研究成果報告書概要(欧文)」より
  • [Publications] Junichi Koike: "Effects of the liquid phase on the high-temperature tensile ductility : from embrittlement to superplastcity" Philosophical Magazine. (in print). (1998)

    • Description
      「研究成果報告書概要(欧文)」より
  • [Publications] Junichi Koike: "Thermal cycling fatigue and deformation mechanism in aluminum alloy thin films on silicon" Journal of Materials Reserch. (in print). (1998)

    • Description
      「研究成果報告書概要(欧文)」より

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Published: 1999-03-16  

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