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 language | English |
|---|---|
| Pages (from-to) | 449-455 |
| Number of pages | 7 |
| Journal | Nippon Kinzoku Gakkaishi/Journal of the Japan Institute of Metals |
| Volume | 76 |
| Issue number | 7 |
| DOIs | |
| Publication status | Published - Jul 2012 |
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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 journal › Article
}
TY - JOUR
T1 - Unprecedented phenomena with tempering of Ti-4Fe-7Al Alloy
AU - Takemoto, Yoshito
AU - Ochi, Masahiro
AU - Senuma, Takehide
AU - Takada, Jun
AU - Shimizu, Ichiro
AU - Matsugi, Kazuhiro
PY - 2012/7
Y1 - 2012/7
N2 - 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.
AB - 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.
KW - Heat treatment
KW - M point
KW - Martensite
KW - Shape recovery
KW - Surface roughness
KW - Variant
UR - http://www.scopus.com/inward/record.url?scp=84865411100&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=84865411100&partnerID=8YFLogxK
U2 - 10.2320/jinstmet.76.449
DO - 10.2320/jinstmet.76.449
M3 - Article
AN - SCOPUS:84865411100
VL - 76
SP - 449
EP - 455
JO - Nippon Kinzoku Gakkaishi/Journal of the Japan Institute of Metals
JF - Nippon Kinzoku Gakkaishi/Journal of the Japan Institute of Metals
SN - 0021-4876
IS - 7
ER -