Microstructure, tensile, and creep behavior of O+BCC Ti2AlNb alloys processed using induction-float-zone melting

C. J. Boehlert, J. F. Bingert

Research output: Research - peer-reviewArticle

  • 18 Citations

Abstract

The microstructure, tensile, and tensile-creep behavior were studied for orthorhombic (O) plus body-centered cubic (BCC) Ti-22Al-24Nb and Ti-26Al-27Nb (at.%) alloys processed using induction-float-zone melting (IFZM). Microstructure studies were performed using scanning and transmission electron microscopy (SEM and TEM), automated electron back-scattered diffraction (EBSD), and X-ray diffraction (XRD). Upon solidification, the BCC phase evolved with [100] oriented nearly parallel to the longitudinal rod direction. During the slow cool through the O+BCC-phase field, O-variants formed in a fine lath network within the parent BCC. The as-processed Ti-26Al-27Nb rod was strongly textured with an approximately equal distribution of six resolvable O-variants. The retained BCC phase, which was sandwiched between O laths, maintained a higher volume fraction (Vf∼0.20) in Ti-22Al-24Nb compared to Ti-26Al-27Nb (Vf∼0.05). The tensile and creep behavior of the as-processed microstructures were evaluated with the tensile axis oriented parallel to the longitudinal rod direction. The fully lath O+BCC Ti-22Al-24Nb microstructure exhibited a room-temperature yield strength of 836 MPa and an elongation-to-failure of 4.5%. Surface slip traces revealed that slip was compatible between the O and BCC phases. An untransformed-BCC Ti-26Al-27Nb microstructure, oriented with [100] nearly parallel to the tensile axis, exhibited localized deformation bands resulting in an elongation of more than 5.9% and an average yield strength of 828 MPa. In terms of the creep behavior, the secondary creep rates revealed that the fully lath O+BCC Ti-26Al-27Nb microstructure significantly outperformed that for all other O-based alloys. For applied stresses greater than 300 MPa, an activation energy of 346 kJ/mol and a creep exponent of 5.1 were measured, while for lower applied stresses the creep exponent transitioned to a value of 2.3. Overall, this work shows that induction-float-zone processing produces textured fully lath O+BCC microstructures containing an attractive balance of room- and elevated-temperature properties for Al concentrations as high as 26 at.%. Crown

LanguageEnglish (US)
Pages400-408
Number of pages9
JournalJournal of Materials Processing Technology
Volume117
Issue number3
DOIs
StatePublished - Nov 23 2001
Externally publishedYes

Profile

Zone melting
Creep
Microstructure
Yield stress
Elongation
Transmission electron microscopy
Scanning electron microscopy
Temperature
Direction compound
Solidification
Volume fraction
Activation energy
Diffraction
X ray diffraction
Electrons
Processing

Keywords

  • Body-centered cubic
  • Creep
  • Induction-float-zone melting
  • Microtexture
  • Orientation relationship
  • Orthorhombic
  • Tension

ASJC Scopus subject areas

  • Materials Science(all)

Cite this

Microstructure, tensile, and creep behavior of O+BCC Ti2AlNb alloys processed using induction-float-zone melting. / Boehlert, C. J.; Bingert, J. F.

In: Journal of Materials Processing Technology, Vol. 117, No. 3, 23.11.2001, p. 400-408.

Research output: Research - peer-reviewArticle

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abstract = "The microstructure, tensile, and tensile-creep behavior were studied for orthorhombic (O) plus body-centered cubic (BCC) Ti-22Al-24Nb and Ti-26Al-27Nb (at.%) alloys processed using induction-float-zone melting (IFZM). Microstructure studies were performed using scanning and transmission electron microscopy (SEM and TEM), automated electron back-scattered diffraction (EBSD), and X-ray diffraction (XRD). Upon solidification, the BCC phase evolved with [100] oriented nearly parallel to the longitudinal rod direction. During the slow cool through the O+BCC-phase field, O-variants formed in a fine lath network within the parent BCC. The as-processed Ti-26Al-27Nb rod was strongly textured with an approximately equal distribution of six resolvable O-variants. The retained BCC phase, which was sandwiched between O laths, maintained a higher volume fraction (Vf∼0.20) in Ti-22Al-24Nb compared to Ti-26Al-27Nb (Vf∼0.05). The tensile and creep behavior of the as-processed microstructures were evaluated with the tensile axis oriented parallel to the longitudinal rod direction. The fully lath O+BCC Ti-22Al-24Nb microstructure exhibited a room-temperature yield strength of 836 MPa and an elongation-to-failure of 4.5%. Surface slip traces revealed that slip was compatible between the O and BCC phases. An untransformed-BCC Ti-26Al-27Nb microstructure, oriented with [100] nearly parallel to the tensile axis, exhibited localized deformation bands resulting in an elongation of more than 5.9% and an average yield strength of 828 MPa. In terms of the creep behavior, the secondary creep rates revealed that the fully lath O+BCC Ti-26Al-27Nb microstructure significantly outperformed that for all other O-based alloys. For applied stresses greater than 300 MPa, an activation energy of 346 kJ/mol and a creep exponent of 5.1 were measured, while for lower applied stresses the creep exponent transitioned to a value of 2.3. Overall, this work shows that induction-float-zone processing produces textured fully lath O+BCC microstructures containing an attractive balance of room- and elevated-temperature properties for Al concentrations as high as 26 at.%. Crown",
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T1 - Microstructure, tensile, and creep behavior of O+BCC Ti2AlNb alloys processed using induction-float-zone melting

AU - Boehlert,C. J.

AU - Bingert,J. F.

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Y1 - 2001/11/23

N2 - The microstructure, tensile, and tensile-creep behavior were studied for orthorhombic (O) plus body-centered cubic (BCC) Ti-22Al-24Nb and Ti-26Al-27Nb (at.%) alloys processed using induction-float-zone melting (IFZM). Microstructure studies were performed using scanning and transmission electron microscopy (SEM and TEM), automated electron back-scattered diffraction (EBSD), and X-ray diffraction (XRD). Upon solidification, the BCC phase evolved with [100] oriented nearly parallel to the longitudinal rod direction. During the slow cool through the O+BCC-phase field, O-variants formed in a fine lath network within the parent BCC. The as-processed Ti-26Al-27Nb rod was strongly textured with an approximately equal distribution of six resolvable O-variants. The retained BCC phase, which was sandwiched between O laths, maintained a higher volume fraction (Vf∼0.20) in Ti-22Al-24Nb compared to Ti-26Al-27Nb (Vf∼0.05). The tensile and creep behavior of the as-processed microstructures were evaluated with the tensile axis oriented parallel to the longitudinal rod direction. The fully lath O+BCC Ti-22Al-24Nb microstructure exhibited a room-temperature yield strength of 836 MPa and an elongation-to-failure of 4.5%. Surface slip traces revealed that slip was compatible between the O and BCC phases. An untransformed-BCC Ti-26Al-27Nb microstructure, oriented with [100] nearly parallel to the tensile axis, exhibited localized deformation bands resulting in an elongation of more than 5.9% and an average yield strength of 828 MPa. In terms of the creep behavior, the secondary creep rates revealed that the fully lath O+BCC Ti-26Al-27Nb microstructure significantly outperformed that for all other O-based alloys. For applied stresses greater than 300 MPa, an activation energy of 346 kJ/mol and a creep exponent of 5.1 were measured, while for lower applied stresses the creep exponent transitioned to a value of 2.3. Overall, this work shows that induction-float-zone processing produces textured fully lath O+BCC microstructures containing an attractive balance of room- and elevated-temperature properties for Al concentrations as high as 26 at.%. Crown

AB - The microstructure, tensile, and tensile-creep behavior were studied for orthorhombic (O) plus body-centered cubic (BCC) Ti-22Al-24Nb and Ti-26Al-27Nb (at.%) alloys processed using induction-float-zone melting (IFZM). Microstructure studies were performed using scanning and transmission electron microscopy (SEM and TEM), automated electron back-scattered diffraction (EBSD), and X-ray diffraction (XRD). Upon solidification, the BCC phase evolved with [100] oriented nearly parallel to the longitudinal rod direction. During the slow cool through the O+BCC-phase field, O-variants formed in a fine lath network within the parent BCC. The as-processed Ti-26Al-27Nb rod was strongly textured with an approximately equal distribution of six resolvable O-variants. The retained BCC phase, which was sandwiched between O laths, maintained a higher volume fraction (Vf∼0.20) in Ti-22Al-24Nb compared to Ti-26Al-27Nb (Vf∼0.05). The tensile and creep behavior of the as-processed microstructures were evaluated with the tensile axis oriented parallel to the longitudinal rod direction. The fully lath O+BCC Ti-22Al-24Nb microstructure exhibited a room-temperature yield strength of 836 MPa and an elongation-to-failure of 4.5%. Surface slip traces revealed that slip was compatible between the O and BCC phases. An untransformed-BCC Ti-26Al-27Nb microstructure, oriented with [100] nearly parallel to the tensile axis, exhibited localized deformation bands resulting in an elongation of more than 5.9% and an average yield strength of 828 MPa. In terms of the creep behavior, the secondary creep rates revealed that the fully lath O+BCC Ti-26Al-27Nb microstructure significantly outperformed that for all other O-based alloys. For applied stresses greater than 300 MPa, an activation energy of 346 kJ/mol and a creep exponent of 5.1 were measured, while for lower applied stresses the creep exponent transitioned to a value of 2.3. Overall, this work shows that induction-float-zone processing produces textured fully lath O+BCC microstructures containing an attractive balance of room- and elevated-temperature properties for Al concentrations as high as 26 at.%. Crown

KW - Body-centered cubic

KW - Creep

KW - Induction-float-zone melting

KW - Microtexture

KW - Orientation relationship

KW - Orthorhombic

KW - Tension

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