Effects of γ/γ interfaces in TiAl lamellae subjected to uniaxial tensile loading

Li, Wen; Yu, Wen Chung; Xu, Qian; Zhou, Jianxin; Hu, Nan; Yin, Yajun; Feng, Xin; Shen, Xu

doi:10.1016/j.commatsci.2019.109361

Cited by 14 publications

(5 citation statements)

References 51 publications

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“…The perpendicular direction to the interface (along

z \left[\right. 111 \left]\right.

) is omitted in this study as the γ phase exhibits a substantially higher strength [ 30,34 ] along this direction and the several associated mechanisms have been previously studied in detail by us. [ 30 ] During loading, a constant strain rate of

\left(10\right)^{8} \text{m} \textrm{ } \left(\text{s}\right)^{- 1}

is imposed along the respective loading direction and pressure is maintained at zero along perpendicular directions.…”

Section: Methodsmentioning

confidence: 99%

“…However, the origins of plasticity in an isolated presence of either coherency stresses or misfit dislocations could not be revealed. In this light, atomistic simulations of TiAl [24,[30][31][32][33][34][35][36][37][38] are a valuable tool to systematically study and DOI: 10.1002/adem.202300121 γ/γ interfaces drive plastic deformation in lamellar TiAl alloys. Due to the ordering and resulting tetragonal nature of γ phase, γ/γ twin interfaces exist as different variants, some of which exhibit coherency stresses or semicoherent interface structures.…”

Section: Introductionmentioning

confidence: 99%

“…However, the origins of plasticity in an isolated presence of either coherency stresses or misfit dislocations could not be revealed. In this light, atomistic simulations of TiAl [ 24,30–38 ] are a valuable tool to systematically study and decouple these aspects. In our previous work, we carried out an atomistic investigation of coherent and semi‐coherent

\left(\alpha\right)_{2} / \gamma

lamellae under deformation and systematically decoupled the effects of volume fraction and layer thickness.…”

Section: Introductionmentioning

confidence: 99%

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How Coherent and Semi‐Coherent Interfaces Govern Dislocation Nucleation in Lamellar TiAl Alloys

Chauniyal

Janisch

2023

Adv Eng Mater

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γ/γ interfaces drive plastic deformation in lamellar TiAl alloys. Due to the ordering and resulting tetragonal nature of γ phase, γ/γ twin interfaces exist as different variants, some of which exhibit coherency stresses or semicoherent interface structures. While geometric parameters, such as the lamella spacing and orientation, are explored extensively in experiments, the isolation of individual influence of different interfaces in a nanolamellar microstructure remains a challenge. Herein, the range of γ/γ interface states is modeled using bilayers of the coherent γ/γTrueTwin, and the coherent or semicoherent γ/γPseudoTwin, and their deformation behavior is compared. It is shown that residual coherency stresses arise due to misfit accommodation in coherent γ/γPT specimens, which causes early preferential nucleation in one γ layer. Similarly, semicoherent specimens show preferential nucleation from misfit dislocations at the interface, which obeys Schmid's rule. In contrast, coherent γ/γTT specimens show no preferential nucleation and therefore exhibit higher strength. Thus, it is demonstrated that the presence of rotational γ/γ interfaces with misfit is responsible for localized and early plasticity, that lowers the strength of a lamellar microstructure. The interface type, which considers the coherency state, is used as a criterion for alloy microstructure design in the future.

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“…The perpendicular direction to the interface (along

z \left[\right. 111 \left]\right.

\left(10\right)^{8} \text{m} \textrm{ } \left(\text{s}\right)^{- 1}

is imposed along the respective loading direction and pressure is maintained at zero along perpendicular directions.…”

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

“…However, the origins of plasticity in an isolated presence of either coherency stresses or misfit dislocations could not be revealed. In this light, atomistic simulations of TiAl [ 24,30–38 ] are a valuable tool to systematically study and decouple these aspects. In our previous work, we carried out an atomistic investigation of coherent and semi‐coherent

\left(\alpha\right)_{2} / \gamma

lamellae under deformation and systematically decoupled the effects of volume fraction and layer thickness.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

How Coherent and Semi‐Coherent Interfaces Govern Dislocation Nucleation in Lamellar TiAl Alloys

Chauniyal

Janisch

2023

Adv Eng Mater

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“…In MD simulations of TiAl, the different intermetallic phases (c and α 2 ) are modeled with their respective crystallographic systems (i.e., γ: face-centered tetragonal and α 2 : hexagonal closepacked) and appropriate orientations as well as with suitable interatomic interaction potentials (Zope and Mishin, 2003;Kim et al, 2016). In recent time, several MD studies have been devoted to deepen our understanding of the deformation behavior of γ-TiAl (Zhou et al, 2004;Xie et al, 2015;Kanani et al, 2016;Wu et al, 2016;Li et al, 2017;Feng et al, 2018;Hui et al, 2018;Cao et al, 2019;Ding et al, 2019;Feng et al, 2019;Li et al, 2019;Li et al, 2020) in combination with experiments. Kanani et al (2016) performed MD shear simulations of a distinct c/c interface, observing different deformation mechanisms and strong in-plane anisotropy of shear strength.…”

Section: Introductionmentioning

confidence: 99%

Quantifying the High-Temperature Separation Behavior of Lamellar Interfaces in γ-Titanium Aluminide Under Tensile Loading by Molecular Dynamics

2021

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γ-titanium aluminide (TiAl) alloys with fully lamellar microstructure possess excellent properties for high-temperature applications. Such fully lamellar microstructure has interfaces at different length scales. The separation behavior of the lamellae at these interfaces is crucial for the mechanical properties of the whole material. Unfortunately, quantifying it by experiments is difficult. Therefore, we use molecular dynamics (MD) simulations to this end. Specifically, we study the high-temperature separation behavior under tensile loading of the four different kinds of lamellar interfaces appearing in TiAl, namely, the γ/α2, γ/γPT, γ/γTT, and γ/γRB interfaces. In our simulations, we use two different atomistic interface models, a defect-free (Type-1) model and a model with preexisting voids (Type-2). Clearly, the latter is more physical but studying the former also helps to understand the role of defects. Our simulation results show that among the four interfaces studied, the γ/α2 interface possesses the highest yield strength, followed by the γ/γPT, γ/γTT, and γ/γRB interfaces. For Type-1 models, our simulations reveal failure at the interface for all γ/γ interfaces but not for the γ/α2 interface. By contrast, for Type-2 models, we observe for all the four interfaces failure at the interface. Our atomistic simulations provide important data to define the parameters of traction–separation laws and cohesive zone models, which can be used in the framework of continuum mechanical modeling of TiAl. Temperature-dependent model parameters were identified, and the complete traction–separation behavior was established, in which interface elasticity, interface plasticity, and interface damage could be distinguished. By carefully eliminating the contribution of bulk deformation from the interface behavior, we were able to quantify the contribution of interface plasticity and interface damage, which can also be related to the dislocation evolution and void nucleation in the atomistic simulations.

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“…Results show that the strengths of the configurations with true twin boundaries and those with ordered domain boundaries are almost the same, while the strength of a configuration with a pseudo-twin boundary is relatively low. Li et al [ 13 ] investigated the influences of γ/γ interfaces on the tensile deformation behavior of γ-TiAl lamellae. Results in this work indicated that adjacent lamellae with a pseudo-twin or rotational boundary interface can constrain each other by in-plane stress due to modulus misfit; thus, the yield strength can be influenced.…”

Section: Introductionmentioning

confidence: 99%

The Effects of Grain Boundary Misorientation on the Mechanical Properties and Mechanism of Plastic Deformation of Ni/Ni3Al: A Molecular Dynamics Study

et al. 2020

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The effects of grain boundary misorientation angle (θ) on mechanical properties and the mechanism of plastic deformation of the Ni/Ni3Al interface under tensile loading were investigated using molecular dynamics simulations. The results show that the space lattice arrangement at the interface is dependent on grain boundary misorientations, while the interfacial energy is dependent on the arrangement. The interfacial energy varies in a W pattern as the grain boundary misorientation increases from 0° to 90°. Specifically, the interfacial energy first decreases and then increases in both segments of 0–60° and 60–90°. The yield strength, elastic modulus, and mean flow stress decrease as the interfacial energy increases. The mechanism of plastic deformation varies as the grain boundary misorientation angle (θ) increases from 0° to 90°. When θ = 0°, the microscopic plastic deformation mechanisms of the Ni and Ni3Al layers are both dominated by stacking faults induced by Shockley dislocations. When θ = 30°, 60°, and 80°, the mechanisms of plastic deformation of the Ni and Ni3Al layers are the decomposition of stacking faults into twin grain boundaries caused by extended dislocations and the proliferation of stacking faults, respectively. When θ = 90°, the mechanisms of plastic deformation of both the Ni and Ni3Al layers are dominated by twinning area growth resulting from extended dislocations.

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Effects of γ/γ interfaces in TiAl lamellae subjected to uniaxial tensile loading

Cited by 14 publications

References 51 publications

How Coherent and Semi‐Coherent Interfaces Govern Dislocation Nucleation in Lamellar TiAl Alloys

How Coherent and Semi‐Coherent Interfaces Govern Dislocation Nucleation in Lamellar TiAl Alloys

Quantifying the High-Temperature Separation Behavior of Lamellar Interfaces in γ-Titanium Aluminide Under Tensile Loading by Molecular Dynamics

The Effects of Grain Boundary Misorientation on the Mechanical Properties and Mechanism of Plastic Deformation of Ni/Ni3Al: A Molecular Dynamics Study

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