Tensile and Creep Behavior of Ordered Orthorhombic Ti<sub>2</sub>A1Nb-Based Alloys

Rowe, R.G.; Konitzer, D.G.; Woodfield, A. P.; Chesnutt, J. C.

doi:10.1557/proc-213-703

Cited by 28 publications

(15 citation statements)

References 2 publications

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“…In this poorer f values. In the case of Ti-12Al-38Nb, O platelets case, the YS value (1294 MPa) taken from a previous study provided significant strengthening for the ␤-dominated of Ti-22Al-27Nb [1] was used. microstructures, with an associated reduction in f .…”

Section: B Elevated-temperature Properties (A)mentioning

confidence: 99%

“…pct) O-based and Ti-27Al-10Nb (at. pct)* ␣ 2 -based alloys and reported that all alloy, [1] the reported ultimate tensile strength (UTS) was as high as 1415 MPa, with f ϭ 3.6 pct (Table I). Other studies *All alloy compositions are given in atomic percent.…”

Section: Introductionmentioning

confidence: 99%

“…which are usually heightened at grain boundaries, and this is partially responsible for the significantly reduced grainboundary cracking at adjacent O/bcc grains compared with Ti-23Al-16Nb [21] 1050 ЊC/1 h/WQ ϩ 850 ЊC/2 h/FC 691 906 14.0 Ti-22Al-23Nb [13] 1050 ЊC/2 h ϩ 815 ЊC/8 h/FC 836 1111 14.8 Ti-23Al-23Nb [16] 760 ЊC/100 h 472 638 4.0 Ti-22Al-20Nb-5V [4] 815 ЊC/24 h ϩ 760 ЊC/100 h 900 1161 18.8 Ti-22Al-24Nb [4] 815 ЊC/4 h 1257 1350 3.6 Ti-22Al-25Nb [1] 1000 ЊC/1 h/Ar ϩ 815 ЊC/2 h/Ar 1245 1415 4.6 Ti-22Al-25Nb [1] 1125 ЊC/1 h/BC ϩ 815 ЊC/2 h/Ar 1134 1175 0.9 Ti-22Al-27Nb [1] 815 ЊC/1 h/Ar 1294 1415 3.6 Ti-25Al-21Nb [1] 1050 ЊC/1 h/Ar ϩ 815 ЊC/2 h/Ar 847 881 0.4 Ti-15Al-45Nb [32] 1050 ЊC/4 h ϩ 800 ЊC/24 h 865 924 15.1 WQ: water quench, FC: furnace cool, Ar: cooling performed in static argon gas, and BC: brick cooled (1.5 ЊC/s). evident in the ␣ 2 and O phases.…”

Section: Introductionmentioning

confidence: 99%

“…Table I lists the RT tensile properties for several Ti-Al-Nb alloys. Rowe [1][2][3][4] has investigated the fracture toughness and RT tensile properties for a series of O ϩ bcc II. EXPERIMENTAL alloys with Al and Nb contents between 21 and 28 at.…”

Section: Introductionmentioning

confidence: 99%

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Part III. The tensile behavior of Ti-Al-Nb O+Bcc orthorhombic alloys

Boehlert

2001

Metall Mater Trans A

144

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The tensile behavior of Ti-Al-Nb alloys with Al concentrations between 12 and 26 at. pct and Nb concentrations between 22 and 38 at. pct has been investigated for temperatures between 25 ЊC and 650 ЊC. Several microstructural features were evaluated in an attempt to identify microstructureproperty relationships. In particular, the effects of the phase volume fraction, composition, morphology, and grain size were examined. In addition, the constitutive properties were evaluated using singlephase microstructures, and the results provided insight into the microstructure-property relationships of the two-phase orthorhombic (O) ϩ body-centered-cubic (bcc) microstructures. The disordered fully-bcc (␤) Ti-12Al-38Nb microstructure, produced through heat treatment above the ␤-transus, exhibited a room-temperature (RT) elongation of more than 27 pct and the lowest yield strength (YS-553 MPa) of all the alloys studied. The ordered fully-bcc (B2) microstructures, produced through supertransus heat treatment of near-Ti 2 AlNb alloys, exhibited fracture strengths up to 672 MPa and low elongations-to-failure ( f Յ 0.6 pct). Thus, increasing the Al content, which favors ordering of the bcc structure, significantly reduces the ductility of the bcc phase. Similar to the ordered B2 microstructure, the ordered fully-O Ti 2 AlNb microstructures exhibited intermediate RT strength (Յ 704 MPa) and f (Յ1 pct). The O ϩ bcc microstructures tended to exhibit strengths greater than both the fully-O and fully-bcc microstructures, and this was attributed to the finer grain sizes in the twophase microstructures compared to their single-phase counterparts. A RT of 1125 MPa was measured for the finest-grained two-phase microstructure. The O ϩ bcc microstructures containing greater bccphase volume fractions tended to exhibit greater elongations yet poorer elevated-temperature strengths. A higher Al content typically resulted in larger elevated-temperature strengths. For the Ti-12Al-38Nb bcc-dominated microstructures, fine O platelets, which precipitated during aging, provided significant strengthening and a reduction in f for the Ti-12Al-38Nb alloy. However, large RT elongations ( f Ͼ 12 pct) were maintained for aged Ti-12Al-38Nb microstructures, which contained 28 vol pct O phase. Morphology did not appear to play a dominant role, as fully-lath and fully-equiaxed two-phase microstructures containing the same phase volume fractions exhibited similar RT tensile properties. The slip and cracking observations provided evidence for the ductile and brittle characteristics of the single-phase microstructures, and the slip compatibility exhibited between the two phases is an important part of why O ϩ bcc microstructures achieve attractive strengths and elongations. The YS vs temperature behavior is discussed in light of other Ti-alloy systems.

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Section: B Elevated-temperature Properties (A)mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Part III. The tensile behavior of Ti-Al-Nb O+Bcc orthorhombic alloys

Boehlert

2001

Metall Mater Trans A

144

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“…Several studies have focused on constructing microstructure-creep relationships and determining creep deformation mechanisms [8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27] and constructing microstructure-tensile relationships of two-phase O + bcc Ti-Al-Nb alloys. [6,8,16,[18][19][20][21][22][23]25,[27][28][29][30][31][32][33] To some extent, the tensile and creep properties of fully-O microstructures and the tensile properties of fully-bcc microstructures have been characterized.…”

Section: Introductionmentioning

confidence: 99%

The Microstructure, Creep, and Tensile Behavior for Ti-5Al-45Nb (Atomic Percent) Fully-β Alloy

Cowen

Boehlert

2007

Metall Mater Trans A

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The microstructure, tensile, and creep behavior of a Ti-5Al-45Nb (at. pct) alloy was evaluated. The main objective of processing and characterizing this alloy was to obtain the constituent properties of a fully-b Ti-Al-Nb alloy to aid in modeling the tensile and creep properties of twophase orthorhombic + body-centered-cubic (O + bcc) alloys. A second objective was to compare the tensile and creep behavior of this fully-b alloy to that for two-phase O + bcc alloys. This alloy exhibited a single-phase microstructure, containing the disordered bcc phase (b), after all the processing and heat treatments performed. This alloy was easily fabricated and workable; however, its creep resistance was significantly worse than that for fully-O and twophase O + bcc alloys. The alloy exhibited little strain hardening along with a room-temperature yield strength (YS) of 545 MPa, an ultimate tensile stress (UTS) of 559 MPa, a YoungÕs modulus (E) of 86 GPa, and a tensile elongation to failure of 25 pct. Extensive surface slip was evident on the deformed material. Its room-temperature tensile properties were quite similar to those for a fully-b Ti-12Al-38Nb microstructure (YS = 553 MPa, UTS = 566 MPa, E = 84, and e f > 27 pct). Thus, the room-temperature tensile properties and behavior of fully-b Ti-AlNb microstructures containing 50 at. pct Ti are not sensitive to compositional variations between 5 to 12 at. pct Al and 38 to 45 at. pct Nb.

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