Thermodynamic and microstructural study of Ti2AlNb oxides at 800 °C

Xiang, Jiayi; Mi, Guangbao; Qu, Shoujiang; Huang, Xu; Chen, Z.; Ai, Feng; Shen, Jun; Chen, D. L.

doi:10.1038/s41598-018-31196-w

Cited by 23 publications

(5 citation statements)

References 49 publications

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“…It is usually assumed that the interface satisfies the stabilizing relationship characteristics when the mismatch is less than 5%. The small interfacial mismatch degree also implies that the B2(110)/O(001) interface is basically coherent, which is often observed in Ti 2 AlNb alloys in experiments [14].…”

Section: Structural Modelsmentioning

confidence: 58%

“…The oxidation process of Ti 2 AlNb alloys is controlled by the microstructure of the initial B2-O two-phase interface, and the extremely lamellar morphology restricts the diffusion of oxygen [13]. In our previous experiments on the oxidation mechanisms of Ti 2 AlNb alloys at 800 • C, the TEM observations revealed that the O phase and B2 phase followed a crystallographic-orientation relationship of [111]B2//[110]O and (110)B2//(001)O [14], which was also observed in other studies related to Ti 2 AlNb alloys [15,16].…”

Section: Introductionmentioning

confidence: 99%

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First-Principles Investigation on the Adsorption and Diffusion of Oxygen at the B2(110)–O(001) Interface in Ti2AlNb Alloys

Zhang,

Xiang,

et al. 2024

Metals

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The adsorption and diffusion of oxygen at the B2(110)[1¯11]||O(001)[11¯0] interface in Ti2AlNb alloys were investigated via first-principles calculations. Only a 2.6% interfacial mismatch indicates that B2(110)–O(001) is basically a stable coherent interface. The calculated adsorption energies and diffusion energy barriers show that oxygen prefers to occupy the Ti-rich interstitial sites, and once trapped, it hardly diffuses to other interstitial sites, thus promoting the preferential formation of Ti oxides. Under the premise of a Ti-rich environment, a Nb-rich environment is more favorable for oxygen adsorption than an Al-rich environment. The electronic structures suggest that O 2p orbitals mainly occupy the energy region below −5 eV, bonding with its coordinated atoms of Ti, Al, and Nb. However, Al 3p and Nb 4d orbitals near the Fermi level couple with sparsely distributed O 2p orbitals, forming anti-bonding, which is not conducive to oxygen adsorption. Because Nb 4d electrons are more localized than Al 3p electrons are, Nb–O anti-bonding is weaker. O–Ti has almost no contribution to anti-bonding, suggesting good bonding between them. This is consistent with the experimental observations that TiO2 is the main oxidation product.

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Section: Structural Modelsmentioning

confidence: 58%

Section: Introductionmentioning

confidence: 99%

First-Principles Investigation on the Adsorption and Diffusion of Oxygen at the B2(110)–O(001) Interface in Ti2AlNb Alloys

Zhang,

Xiang,

et al. 2024

Metals

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“…Moreover, even though the L-PBF process is carried out under an inert atmosphere, some oxygen pickup by the alloy is still possible due to high temperatures. It is also known that the diffusion of oxygen at the phase boundary is faster as a result of the presence of phase/grain boundary energy [52]. This results in increased oxygen content in the grain boundary O-phase leading to its further embrittlement.…”

Section: L-pbf Processabilitymentioning

confidence: 99%

Processing, Microstructure, and Mechanical Properties of Laser Additive Manufactured Ti2AlNb-Based Alloy with Carbon, Boron, and Yttrium Microalloying

Polozov

Gracheva

Popovich

2022

Metals

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In this work, Ti-22Al-23Nb-0.8Mo-0.3Si-0.4C-0.1B-0.2Y (at. %) alloy powder was used to fabricate the Ti2AlNb-based alloy samples using Laser powder bed fusion (L-PBF) Additive Manufacturing with a high-temperature substrate preheating. L-PBF process parameters, including laser power, scan speed, hatching distance, and preheating temperature, allowing for obtaining fully dense (99.9% relative density) crack-free samples, were determined. The effects of substrate preheating temperature during the L-PBF process on microstructure, phase composition, and properties of the obtained Ti2AlNb-based alloy were investigated using X-ray diffraction, scanning electron microscopy, electron backscatter diffraction analysis, and microhardness testing. The results obtained for the material with C, B, and Y microalloying were compared to the Ti2AlNb-based alloy fabricated by L-PBF from the powder not alloyed with C, B, and Y. The results revealed that the microalloying reduced the number of solidification cracks; however, no significant microstructural changes were observed, and high-temperature substrate preheating was still necessary to suppress cold cracking of the alloy. The microstructure of the alloy varied from fully-β/B2, B2 + O, to fully-O depending on the preheating temperature. Effects of hot isostatic pressing and heat treatment conditions on microstructure and mechanical properties were investigated.

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“…In order to achieve the service requirements of modern aero-engines and further improve their various properties, the Ti 2 AlNb alloy was developed by adding Nb to the Ti 3 Al-based alloy [11,12]. The element Nb not only inhibits the oxidation of Ti, but also increases the activity of Al, enabling the alloy to preferentially produce stable Al 2 O 3 at high temperatures [13][14][15]. Therefore, Ti 2 AlNb alloy is expected to be the primary material used for making aero-engine hot-end components.…”

Section: Introductionmentioning

confidence: 99%

Oxidative Corrosion Mechanism of Ti2AlNb-Based Alloys during Alternate High Temperature-Salt Spray Exposure

et al. 2022

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This study investigates the corrosion damage mechanisms of Ti2AlNb-based alloys under high temperature, salt spray and coupled high temperature-salt spray conditions. This alloy was analysed in detail from macroscopic to microscopic by means of microscale detection (XRD, SEM and EDS). The results indicated that Ti2AlNb-based alloy surface oxide layer is dense and complete, and the thickness is only 3 µm after oxidation at 650 °C for 400 h. Compared to the original sample, the production of the passivation film resulted in almost no damage to Ti2AlNb-based alloy after 50 cycles of salt spray testing at room temperature. The tests showed that Ti2AlNb alloy shows good erosion resistance at 650 °C and in salt spray. However, this alloy had an oxide layer thickness of up to 30 µm and obvious corrosion pits on the surface after 50 cycles of corrosion under alternating high temperature-salt spray conditions. The Cl2 produced by the mixed salt eutectic reaction acted as a catalytic carrier to accelerate the volatilisation of the chloride inside the oxide layer and the re-oxidation of the substrate. In addition, the growth of unprotected corrosion products (Na2TiO3, NaNbO3 and AlNbO4) altered the internal structure of the oxide layer, destroying the surface densification and causing severe damage to the alloy surface.

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Thermodynamic and microstructural study of Ti2AlNb oxides at 800 °C

Cited by 23 publications

References 49 publications

First-Principles Investigation on the Adsorption and Diffusion of Oxygen at the B2(110)–O(001) Interface in Ti2AlNb Alloys

First-Principles Investigation on the Adsorption and Diffusion of Oxygen at the B2(110)–O(001) Interface in Ti2AlNb Alloys

Processing, Microstructure, and Mechanical Properties of Laser Additive Manufactured Ti2AlNb-Based Alloy with Carbon, Boron, and Yttrium Microalloying

Oxidative Corrosion Mechanism of Ti2AlNb-Based Alloys during Alternate High Temperature-Salt Spray Exposure

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