Diffusion of oxygen in the Al2O3 oxidation product of TiAl3

Reddy, Ramana G.; Wen, Xiaoli; Okafor, I. C. I.

doi:10.1007/s11661-000-0081-7

Cited by 25 publications

(11 citation statements)

References 8 publications

(11 reference statements)

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“…However, differences in the experimental methods, conditions, and samples resulted in large scatter of the E a . The E a of this study is much higher than that (about 225 kJ mol 1 / calculated for pack aluminization coatings on IMI-834 alloy [10] under cyclic oxidation, but is somewhat lower than that (about 338 kJ mol 1 / calculated for oxygen diffusion in alumina layer formed on TiAl 3 [34]. …”

Section: Effect Of the Coating/ta15 On The High Temperature Oxidationcontrasting

confidence: 72%

Hot-dip Aluminizing Fabrication of TiAl3 Coating on TA15 Alloy and Its High Temperature Oxidation Behaviors

Zhang¹,

Peng²,

Mao³

et al. 2011

High Temperature Materials and Processes

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A TiAl 3 -rich coating was developed by hot-dip aluminizing method and subsequent interdiffusion treatment on Ti-6.5Al-1Mo-1V-2Zr (mass %) alloy for high temperature resistance. Interrupted oxidation at temperatures from 973 to 1173 K and isothermal oxidation at temperatures from 923 to 1073 K of the TiAl 3 -rich coating were conducted. The coating markedly decreased the oxidation rate in comparison with the substrate alloy at 1073 K and lower during the interrupted oxidation, and a layered structure of Al 2 O 3 /TiAl 3 /TiAl 2 /TiAl/alloy from the outside to the inside formed after oxidation at 973 K without changing the main body of the TiAl 3 -rich coating. The oxidation kinetics followed parabolic relations during the stable state stage of the isothermal oxidation; the activation energy for oxidation of the coating was calculated as 323 kJ mol 1 . The hot-dip aluminizing coating provided high protectiveness for the Ti-6.5Al-1Mo-1V-2Zr alloy at 973 K and lower. The oxidation performance of the TiAl 3 -rich coating was discussed in detail.Keywords. Ti-6.5Al-1Mo-1V-2Zr, high temperature oxidation, hot-dip aluminizing, activation energy.

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Section: Effect Of the Coating/ta15 On The High Temperature Oxidationcontrasting

confidence: 72%

Hot-dip Aluminizing Fabrication of TiAl3 Coating on TA15 Alloy and Its High Temperature Oxidation Behaviors

Zhang¹,

Peng²,

Mao³

et al. 2011

High Temperature Materials and Processes

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“…11 Further, previous reports on the oxidation of Al-rich Al-Ti cast alloys 12,13 indicate that a-Al 2 O 3 is the only alumina phase present in the scale. Conversely, the scale of mechanically alloyed powders is reported to consist of c-Al 2 O 3 and TiO 2 at the outer surface and c-Al 2 O 3 near the alloy as a protective layer.…”

Section: Introducionmentioning

confidence: 92%

Oxidation of Mechanically Alloyed Al-rich Al–Ti Powders

2006

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The oxidation behavior of Al-rich, metastable mechanically alloyed powders in the Al-Ti binary system has been examined in the context of their potential application in high-energy-density materials. Scanning calorimetry and thermogravimetric analysis in an oxygen atmosphere up to 1500°C have been performed on powders, synthesized with compositions ranging from Al 0.95 Ti 0.05 to Al 0.75 Ti 0.25 . Oxidation proceeds in three distinguishable steps, similar to the oxidation steps observed for pure aluminum. The steps become less pronounced with increasing Ti concentration. For both the first and second oxidation steps, the apparent activation energies are close to 400 kJ/mol. Partially oxidized material was recovered from intermediate temperatures for quantitative phase analysis by X-ray diffraction, Al 2 O 3 and TiO 2 are the main oxidation products. Similarly to pure aluminum, metastable c-alumina is present at temperatures below $ 1000°C, suggesting that the stepwise oxidation is related to phase transitions of the alumina in the oxide scale. At temperatures above 1300°C, oxidation follows melt formation in the binary Al-Ti system, as the aluminum component oxidizes selectively, leaving a titanium-rich metallic residue. No correlation was observed between the oxidation and melting of aluminum.

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“…[35] The conventional form of Darken's equation is given in Eq. [4], which relates the interdiffusion coefficient of an alloy AB as a function of intrinsic …”

Section: Diffusion Analysismentioning

confidence: 99%

“…It is well known that TiAl 3 favors the formation of a continuous a-Al 2 O 3 protective scale, while TiAl has lower activation energy for the oxidation and Ti 3 Al has very poor oxidation resistance at high temperatures. [4][5][6] Although TiAl 3 forms an alumina layer on oxidation, the brittle nature of the oxide layer owing to the mismatch of thermal expansion coefficients between the base alloy and the oxide has led to the research on oxidation resistance of Ti 3 Al intermetallic phase for high-temperature applications. In addition, Ti 3 Al has the highest solubility of oxygen, [7] which also stabilizes the a 2 phase.…”

Section: Introductionmentioning

confidence: 99%

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Oxidation and Diffusion in Ti-Al-(Mo, Nb) Intermetallics

Ramachandran

Mantha

Williams

et al. 2010

Metall Mater Trans A

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The oxidation resistance of Ti-Al intermetallics is superior to many of their counterparts at high temperatures. High-temperature stability of these intermetallics appears to improve with a ternary alloying addition such as Mo, Nb, etc. A detailed analysis of oxidation of the Ti 3 Al intermetallics, Ti 3 Al-2.9 at. pct Mo and Ti 3 Al-1.1 at. pct Nb, in pure oxygen using crystallographic and microscopic techniques is presented here. The alloy containing 1.1 at. pct Nb did not show an improvement in oxidation resistance over the base alloy but that containing 2.9 at. pct Mo showed marked resistance to oxidation. Activation energies of oxidation for both the alloys were comparable with those reported in the literature for similar compositions. TiO 2 and Al 2 O 3 were the major phases present in the oxide scales of the oxidized alloys. The crystal orientations from the X-ray diffraction (XRD) patterns and the morphologies from scanning electron microscopy (SEM) were in good agreement and were helpful in further analysis of the oxidation process. The effective diffusion of oxygen in the oxide layers was calculated using the mole fraction of individual oxide and the diffusivity of oxygen in pure oxide. The activation energy for the effective diffusion of oxygen through the oxide layers was determined to bẽ 24 kJ/mol. The activation energy for the oxidation process was higher than that of the diffusion of oxygen. Hence, it can be concluded that the oxidation process in both the alloys studied is not diffusion controlled.

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Diffusion of oxygen in the Al2O3 oxidation product of TiAl3

Cited by 25 publications

References 8 publications

Hot-dip Aluminizing Fabrication of TiAl3 Coating on TA15 Alloy and Its High Temperature Oxidation Behaviors

Hot-dip Aluminizing Fabrication of TiAl3 Coating on TA15 Alloy and Its High Temperature Oxidation Behaviors

Oxidation of Mechanically Alloyed Al-rich Al–Ti Powders

Oxidation and Diffusion in Ti-Al-(Mo, Nb) Intermetallics

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