The native point defects in C14 Mg2Ca Laves phase: A first-principles study

Shao, Lin; Shi, Tao-Tao; Zheng, Jie; Pan, Xiong-Ze; Tang, Bi‐Yu

doi:10.1016/j.intermet.2015.05.010

Cited by 8 publications

(4 citation statements)

References 48 publications

(29 reference statements)

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“…At 260 °C, the hcp Mg still forms as a second phase in addition to the intermetallic Mg 2 Ca phase with a maximum Mg solubility, as modeled in the FTlite database [ 24 ], while above this temperature, a continuous transition from Mg-rich Mg 2 Ca to Ca-rich Mg 2 Ca is observed upon rising temperature. The performed calculations demonstrate that, based on the thermochemical modeling in the FTlite database [ 24 ] as (Mg, Ca) 2 (Mg, Ca, vacancy), this transition is mainly driven by anti-site defects; this finding is in agreement with the defect-formation energies calculated using density functional theory [ 28 ]. Hence, the decrease in the Mg concentration in the phase-pure Mg 2 Ca yields a decrease in the Mg vapor pressure ( Figure 3 c) and, thus, compensated for the temperature-induced increase in the sublimation flux naturally occurring with the rising temperature.…”

Section: Resultssupporting

confidence: 74%

CALPHAD-Based Modelling of the Temperature–Composition–Structure Relationship during Physical Vapor Deposition of Mg-Ca Thin Films

et al. 2023

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The temperature-dependent composition and phase formation during the physical vapor deposition (PVD) of Mg-Ca thin films is modeled using a CALPHAD-based approach. Considering the Mg and Ca sublimation fluxes calculated based on the vapor pressure obtained by employing thermochemical equilibrium calculations, the experimentally observed synthesis-temperature trends in the thin-film composition and phase formation were reproduced. The model is a significant step towards understanding how synthesis parameters control composition and, therefore, phase formation in the PVD of metals with high vapor pressures.

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Section: Resultssupporting

confidence: 74%

CALPHAD-Based Modelling of the Temperature–Composition–Structure Relationship during Physical Vapor Deposition of Mg-Ca Thin Films

et al. 2023

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“…Although clear experimental evidence is lacking, first-principles calculations on MgCu 2 also suggest predominance of constitutional antisite atoms as compared to constitutional vacancies [132]. Among Laves phases with A being a main-group metal, comparable computational investigations exist for CaAl 2 [133] and CaMg 2 [134], but again with little experimental evidence. predicted from experimentally determined lattice parameters and from different models for constitutional point defects (S: substitutional, V: constitutional vacancies, T and DT: substitution models involving substitution of Zn 4 tetrahedra by Mg atoms and vice versa).…”

Section: Constitutional Point Defectsmentioning

confidence: 98%

Laves phases: a review of their functional and structural applications and an improved fundamental understanding of stability and properties

2020

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Laves phases with their comparably simple crystal structure are very common intermetallic phases and can be formed from element combinations all over the periodic table resulting in a huge number of known examples. Even though this type of phases is known for almost 100 years, and although a lot of information on stability, structure, and properties has accumulated especially during the last about 20 years, systematic evaluation and rationalization of this information in particular as a function of the involved elements is often lacking. It is one of the two main goals of this review to summarize the knowledge for some selected respective topics with a certain focus on non-stoichiometric, i.e., non-ideal Laves phases. The second, central goal of the review is to give a systematic overview about the role of Laves phases in all kinds of materials for functional and structural applications. There is a surprisingly broad range of successful utilization of Laves phases in functional applications comprising Laves phases as hydrogen storage material (Hydraloy), as magneto-mechanical sensors and actuators (Terfenol), or for wear- and corrosion-resistant coatings in corrosive atmospheres and at high temperatures (Tribaloy), to name but a few. Regarding structural applications, there is a renewed interest in using Laves phases for creep-strengthening of high-temperature steels and new respective alloy design concepts were developed and successfully tested. Apart from steels, Laves phases also occur in various other kinds of structural materials sometimes effectively improving properties, but often also acting in a detrimental way.

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“…Point defects, including vacancies and antisite atoms, very commonly exist in Laves phases and have significant effects on mechanical properties [3,15]. For the Mg-Al-Ca alloying system, first-principles calculations on stoichiometric C14 CaMg 2 [39] and C15 CaAl 2 [40] suggest the predominance of constitutional antisite and vacancy defects, respectively.…”

Section: B Point-defect-assisted Dislocation Motionmentioning

confidence: 99%

Unveiling the mechanisms of motion of synchro-Shockley dislocations in Laves phases

Xie

Chauraud

Atila

et al. 2023

Phys. Rev. Materials

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In Laves phases, synchroshear is the dominant basal slip mechanism. It is accomplished by the glide of synchro-Shockley dislocations. However, the atomic-scale mechanisms of motion of such zonal dislocations are still not well understood. In this paper, using atomistic simulations, two 30 • synchro-Shockley dislocations with different Burgers vectors and core structures and energies are identified. We demonstrate that nucleation and propagation of kink pairs is the energetically favorable mechanism for the motion of the synchro-Shockley dislocation (partial I). Vacancy hopping and interstitial shuffling are identified as two key mechanisms related to kink propagation, and we investigated how vacancies and antisite defects assist kink nucleation and propagation, which is crucial for kink mobility. Additionally, we identified a mechanism of nonsequential atomic shuffling for the motion of the synchro-Shockley dislocation (partial II). These findings provide insights into the dependency on temperature and chemical composition of plastic deformation induced by zonal dislocations in Laves phases and the many related topologically close-packed phases.

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The native point defects in C14 Mg2Ca Laves phase: A first-principles study

Cited by 8 publications

References 48 publications

CALPHAD-Based Modelling of the Temperature–Composition–Structure Relationship during Physical Vapor Deposition of Mg-Ca Thin Films

CALPHAD-Based Modelling of the Temperature–Composition–Structure Relationship during Physical Vapor Deposition of Mg-Ca Thin Films

Laves phases: a review of their functional and structural applications and an improved fundamental understanding of stability and properties

Unveiling the mechanisms of motion of synchro-Shockley dislocations in Laves phases

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