Light impurity effects on the electronic structure in TiAl

Dang, Hongli; Wang, C Y; Yu, Tao

doi:10.1088/0953-8984/18/39/011

Cited by 9 publications

(11 citation statements)

References 35 publications

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“…According to recent first-principle calculations boron prefers to occupy the Ti-rich octahedral interstitial sites in gTiAl [45]. This feature agrees well with its fast diffusivity in this alloy established in the present paper.…”

Section: Discussionsupporting

confidence: 92%

“…The long-range diffusion of boron should involve successive jumps of solute atoms between the favorable Ti-rich and unfavorable Al-rich interstitial sites. The energy difference for boron atoms occupying these two sites in g-TiAl was computed to be quite large, about 100 kJ mol À1 [45]. Such a significant difference may qualitatively explain the relatively large activation enthalpy of boron diffusion in g-TiAl, about 200 kJ mol À1 , Eq.…”

Section: Discussionmentioning

confidence: 92%

“…The corresponding activation enthalpy of about 200 kJ mol À1 is fairly large for an interstitial diffusion mechanism. This fact can be explained by a low probability of boron occupation of the Al-rich interstitial sites [45] which have to be visited in the course of the long-range diffusion process.…”

Section: Discussionmentioning

confidence: 99%

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Tracer diffusion of boron in α-Ti and γ-TiAl

et al. 2008

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Section: Discussionsupporting

confidence: 92%

Section: Discussionmentioning

confidence: 92%

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Tracer diffusion of boron in α-Ti and γ-TiAl

et al. 2008

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“…By adding an appropriate amount of transition elements such as V, Mn, Nb, and W to replace Al atoms in TiAl, the interaction between Ti and transition alloy elements can be enhanced and the ductility can be improved [3]. By adding interstitial solid solution elements B, C, and N, the directionality of the nearest Ti-Ti bond can be enhanced, while the interstitial elements H and O can weaken the directionality of the Ti-Ti bond [4]. Therefore, B, C, and N can improve the ductility of TiAl, while H and O cannot [4].…”

Section: Introductionmentioning

confidence: 99%

Influences of Multicenter Bonding and Interstitial Elements on Twinned γ-TiAl Crystal

Wang

et al. 2020

Materials

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The bonding properties of the twin boundary in polysynthetic twinned γ-TiAl crystal and the effect of interstitial alloy elements on it are investigated by first principles. Among the three different kinds of interface relationships in the γ/γ interface, the proportion of true twin boundaries is the highest because it has the lowest interfacial energy, the reason for which is discussed by local energy and three-center bond. The presence of the interstitial atoms C, N, H, and O induces the competition for domination between their affinity to host atoms and three-center bonds, which eventually influences the values of unstable stacking fault energy (USFE) and intrinsic stacking fault energy (ISFE). The relative importance of different bonding with different alloy elements is clarified based on the analysis of local energy combined with Electron Localization Function (ELF) and Quantum Theory of Atoms in Molecules (QTAIM) schemes.

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“…Theoretically, the occupation competition between O and H has been studied [16], and O has been revealed to have a more crucial effect on the environmental embrittlement in comparison with H. The effect of H on the electronic structure has been investigated, and the localized effect of H has been found to be not beneficial to the ductility of   -TiAl [17].…”

mentioning

confidence: 99%

A first-principles study of site occupancy and interfacial energetics of an H-doped TiAl-Ti3Al alloy

Wei

Zhang

Lü

et al. 2012

Sci. China Phys. Mech. Astron.

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We investigate the site occupancy and the interfacial energetics of TiAl-Ti 3 Al binary-phase system with H using a first-principles method. H energetically prefers to occupy the Ti-rich octahedral interstitial site because H prefers to bond with Ti rather than with Al. The occupancy tendency of H in the binary phase TiAl-Ti 3 Al alloy from high to low is  2 -Ti 3 Al to   / 2 interface and -TiAl, because the decrease of the Ti local concentration is in the same order. We demonstrate that H can largely affect the mechanical properties of the TiAl-Ti 3 Al system. On the one hand, H at the interface reduces the interface energy with the H 2 molecule as a reference, implying the TiAl/Ti 3 Al interface is stabilized. On the other hand, the ratio between the cleavage energy and the unstable stacking fault energy decreases after H-doping, indicating H will reduce the ductility of the TiAl/Ti 3 Al interface. Consequently, the mechanical property variation of TiAl alloy due to the presence of H not only depends on the amount of TiAl/Ti 3 Al interfaces but also is related to the H concentration in the alloy.TiAl alloys have great potential for aerospace applications because of their high melting temperature, low density, high modulus, good oxidation and creep resistance. However, their low ductility and toughness at room temperature limit the applications [1]. Research currently focuses on improving ductility and toughness at room temperature of TiAl alloys while maintaining its attractive high temperature characteristics. As a second phase of the -TiAl based alloys, the addition of  2 -Ti 3 Al is capable of improving the ductility of TiAl [2][3][4][5]. The interest in the binary-phase TiAlTi 3 Al alloys is further encouraged because of their superior specific strength and oxidation resistance [6,7]. It is significant to reveal the mechanical property of the TiAl/Ti 3 Al interface to find a way to further improve the ductility of the TiAl alloys.It is generally accepted that a trace amount (ppm) of impurity will result in an obvious variation of mechanical properties of materials [8][9][10][11][12]. H is a typical impurity that degrades the mechanical properties of metals. For example, H-induced embrittlement of metals has been studied from early last century, but the embrittlement mechanism is still not fully understood. The H-induced embrittlement has been explained by various mechanisms [13], such as precipitation of H 2 gas, formation of hydrides, deformation localization, and reduction of cohesion across the grain boundary.Experimentally, H has been demonstrated to embrittle the TiAl alloy [14,15]. On the one hand, several hydrides were reported in TiAl intermetallics [14], and the formation of such hydrides results in an increase in yield stress and a decrease in plasticity and fracture toughness because hydride is a brittle phase. On the other hand, H atoms can be

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Light impurity effects on the electronic structure in TiAl

Cited by 9 publications

References 35 publications

Tracer diffusion of boron in α-Ti and γ-TiAl

Tracer diffusion of boron in α-Ti and γ-TiAl

Influences of Multicenter Bonding and Interstitial Elements on Twinned γ-TiAl Crystal

A first-principles study of site occupancy and interfacial energetics of an H-doped TiAl-Ti3Al alloy

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