Unprecedented phenomena with tempering of Ti-4Fe-7Al Alloy

Yoshito Takemoto, Masahiro Ochi, Takehide Senuma, Jun Takada, Ichiro Shimizu, Kazuhiro Matsugi

Research output: Contribution to journalArticle

11 Citations (Scopus)

Abstract

Unprecedented phenomena were discovered by tempering the Ti-4Fe-7Al alloy quenched from the βß (bec) field. The alloy became very hard when it was tempered at 450°C for several minutes, and severely rugged surface was generated. The inverse shape recovery phenomenon was also discovered when a quenched specimen that had been bent at room temperature was heated. The tempered microstructure showed almost β grains and some of the usual martensitic acicular structure areas. However, elec- tron back scattering pattern (EBSP) measurements showed that the β-like grain was not the bcc structure but was the hcp or orthorhombic structure. X-ray diffraction (XRD) measurements clarified that an orthorhombic α" structure (a = 0.299 5 nm, b = 0.491 3 nm, c=0.465 9 nm) was formed from the β phase by tempering. Moreover, this α" structure was confirmed to be a type of martensitic transformation because no concentration distribution was detected in scanning transmission electron microscopy-energy dispersive spectroscopy (STEM-EDS) analysis of the microstructure. It was suggested that the essential M s point of the alloy should be higher than room temperature; however, the martensite transformation could not operate by fast quenching. The newly-discovered α martensite is formed without atomic diffusion by heating. When the β grain transforms into the single α-variant, a very huge lattice strain is generated, resulting in the severely rugged surface or the inverse shape recovery phenomenon.

Original languageEnglish
Pages (from-to)449-455
Number of pages7
JournalNippon Kinzoku Gakkaishi/Journal of the Japan Institute of Metals
Volume76
Issue number7
DOIs
Publication statusPublished - Jul 2012

Fingerprint

tempering
Tempering
martensite
Martensite
recovery
Recovery
microstructure
Microstructure
Martensitic transformations
martensitic transformation
room temperature
Energy dispersive spectroscopy
Quenching
quenching
Scattering
Transmission electron microscopy
Heating
X ray diffraction
Temperature
transmission electron microscopy

Keywords

  • Heat treatment
  • M point
  • Martensite
  • Shape recovery
  • Surface roughness
  • Variant

ASJC Scopus subject areas

  • Mechanics of Materials
  • Materials Chemistry
  • Metals and Alloys
  • Condensed Matter Physics

Cite this

Unprecedented phenomena with tempering of Ti-4Fe-7Al Alloy. / Takemoto, Yoshito; Ochi, Masahiro; Senuma, Takehide; Takada, Jun; Shimizu, Ichiro; Matsugi, Kazuhiro.

In: Nippon Kinzoku Gakkaishi/Journal of the Japan Institute of Metals, Vol. 76, No. 7, 07.2012, p. 449-455.

Research output: Contribution to journalArticle

Takemoto, Yoshito ; Ochi, Masahiro ; Senuma, Takehide ; Takada, Jun ; Shimizu, Ichiro ; Matsugi, Kazuhiro. / Unprecedented phenomena with tempering of Ti-4Fe-7Al Alloy. In: Nippon Kinzoku Gakkaishi/Journal of the Japan Institute of Metals. 2012 ; Vol. 76, No. 7. pp. 449-455.
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