Transformations in a Ti-24AI-15Nb alloy: Part I. Phase equilibria and microstructure

Muraleedharan, K.; Gogia, A.K.; Nandy, T.K.; Banerjee, D.; Lele, S.

doi:10.1007/bf02801158

Cited by 125 publications

(41 citation statements)

References 12 publications

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“…Note that O phase formed preferentially as a rim around the ␣ 2 phase (inset in Figure 2(e)), suggesting once again that some ␣ 2 phase may have been present in the as-rolled microstructure. The 'rim O' phase is similar to that in three-phase microstructures of other O alloys, [1,12,16] except that this phase was much thicker for the current material.…”

Section: Methodsmentioning

confidence: 92%

“…Further work ment, is extremely stable and resistant to transformation at lower temperatures. [12,16] On the other hand, the decomposito understand this behavior is intended. tion of the B2 phase, although slow, is relatively rapid com-2.…”

Section: B Aging Of Super-transus-treated Materialsmentioning

confidence: 99%

“…with a significant volume fraction of O phase have shown Several works have discussed the phase equilibria of O attractive mechanical properties, [3][4][5][6][7][8][9][10] owing to the excellent alloys. [9][10][11][12][13][14][15][16][17][18][19] Several of these studies have focused on the creep resistance of the O phase combined with some roomlower-temperature stability and aging transformation behavtemperature (RT) ductility of the O phase arising from the ior. [9,10,13,[15][16][17][18][19] Past investigations revealed that alloy compoexistence of multiple slip systems.…”

Section: Introductionmentioning

confidence: 99%

“…Solution-treatment temperatures were (c) 1090 ЊC, (d ) 1025 ЊC, (e) 1000 ЊC, and ( f ) 900 ЊC.range defining the various phase fields, the as-rolled material Although the B2 and ␣ 2 phases had the equiaxed morphology typical of primary grains, several neighboring grains exwas solutionized at different temperatures and then water quenched.Figures 2(c)through (f) illustrate some of the hibited an orientation relationship (OR) of[11][12][13][14][15][16][17][18][19][20]␣ 2 //[1][2][3][4][5][6][7][8][9][10][11]B2, (0001)␣ 2 //(011)B2, which is the well-known microstructures obtained. In these BSD images, the light, gray, and dark regions correspond to the B2, O, and ␣ 2…”

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confidence: 99%

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Part I. The microstructural evolution in Ti-Al-Nb O+Bcc orthorhombic alloys

Boehlert

Majumdar

Seetharaman

et al. 1999

Metall Mater Trans A

272

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Phase transformations and the resulting microstructural evolution of near-Ti 2 AlNb and Ti-12Al-38Nb O ϩ bcc orthorhombic alloys were investigated. For the near-Ti 2 AlNb alloys, the processing temperatures were below the bcc transus, while, for Ti-12Al-38Nb, the processing temperature was supertransus. Phase evolution studies showed that these alloys contain several constituent phases, namely, bcc, O, and ␣ 2 ; when present, the latter was in small quantities compared to the other phases. The transmission electron microscopy (TEM), scanning electron microscopy (SEM), and Xray investigations of samples that were solutionized and water quenched were used to estimate the phase fields, and a pseudobinary diagram based on Ti ϭ 50 at. pct was modified. The agingtransformation behavior was studied in detail. For solutionizing temperatures between 875 ЊC and the bcc transus, the phase composition and volume fraction of the near-Ti 2 AlNb alloys adjusted through relative size changes of the equiaxed B2, O, and ␣ 2 grains. The aging behavior followed three distinct transformation modes, dependent on the solutionizing and aging temperatures. Widmanstätten formation was observed when a new phase evolved from a parent phase. Thus, Widmanstätten O phase precipitated within the B2 phase for supertransus fully B2 microstructures, as well as for subtransus ␣ 2 ϩ B2 microstructures. Similarly, Widmanstätten B2 phase can form from a fully O microstructure, a transformation that has not been observed before. In the case of equiaxed O ϩ B2 solutionized and water-quenched microstructures, Widmanstatten O-phase formation occurred only below 875 ЊC. For the subtransus-solutionized and water-quenched microstructures, a second aging transformation mode, cellular precipitation, was dominant below 750 ЊC. This involved formation of coarse and lenticular O phase that grew into the prior B2 grains from the grain boundaries. A third transformation mode involved composition-invariant transformation, where the fully B2 supertransussolutionized and water-quenched microstructure transformed to a fully O microstructure at 650 ЊC. This microstructure reprecipitated B2 phase out of the O phase with continued aging time. For Ti12Al-38Nb, Widmanstätten O precipitation remained the only transformation mode. It is shown that subtransus processing offers flexibility in controlling microstructures through postprocessing heat treatments.

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Section: Methodsmentioning

confidence: 92%

Section: B Aging Of Super-transus-treated Materialsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

mentioning

confidence: 99%

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Part I. The microstructural evolution in Ti-Al-Nb O+Bcc orthorhombic alloys

Boehlert

Majumdar

Seetharaman

et al. 1999

Metall Mater Trans A

272

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“…pct Al-10 pct Nb-3 pct V-1 pct Mo), the T O-D is in the temperature range of 1100 °C to 1200 °C. [6][7][8][9] Since the volume fractions of the ␣ 2 and ␤ phases play an important role in superplasticity, the measured relative volume fractions in the current super ␣ 2 alloy in consistence with the equilibrium phase diagram are shown in Figure 1(c).…”

Section: Introductionmentioning

confidence: 99%

Texture evolution and mechanical anisotropy in dual-phase Ti3Al-based alloy loaded at 700 °C to 1000 °C

Yang

Huang

Wang

2004

Metall Mater Trans A

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The super ␣ 2 Ti 3 Al-based alloy with a fine grain size of ϳ2.2 m exhibits superplastic elongations over 1000 pct at 920 °C to 1000 °C, 600 pct at 900 °C, 330 pct at 850 °C, and 140 pct at 750 °C. Mechanical anisotropy is observed in this alloy, and relatively lower flow stresses and higher tensile elongations are obtained in the 45 deg specimen loaded at 25 °C to 960 °C. The texture characteristics appear to impose significant influence on the mechanical anisotropy at temperatures below 900°C (under the dislocation creep condition), and the and {0001} basal textures evolve in the ␤ and ␣ 2 phases after tensile straining. At loading temperatures higher than 900 °C (under the superplastic flow condition), the anisotropy effect is less pronounced and the grain orientation distribution becomes basically random in nature. Rationalizations for the mechanical anisotropy in terms of the Schmid factor calculations for the major and minor texture components in the ␤ and ␣ 2 phases provide consistent explanations for the deformation behavior at lower temperatures as well as the initial straining stage at higher temperatures. {111}Ͻ21 1Ͼ

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Intermetallics

Sauthoff

2006

Materials Science and Technology

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Transformations in a Ti-24AI-15Nb alloy: Part I. Phase equilibria and microstructure

Cited by 125 publications

References 12 publications

Part I. The microstructural evolution in Ti-Al-Nb O+Bcc orthorhombic alloys

Part I. The microstructural evolution in Ti-Al-Nb O+Bcc orthorhombic alloys

Texture evolution and mechanical anisotropy in dual-phase Ti3Al-based alloy loaded at 700 °C to 1000 °C

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