Phase stability of bcc Zr in Nb/Zr thin film multilayers

Thompson, Gregory B.; Banerjee, Rajarshi; Dregia, S.A.; Fraser, Hamish L.

doi:10.1016/s1359-6454(03)00380-x

Cited by 55 publications

(37 citation statements)

References 13 publications

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“…8 The change in phase stability of Zr from hexagonal-close-packed (hcp) to bcc, established by electron diffraction in the previous paper, 8 has been confirmed in this report by the use of transmission x-ray diffraction (XRD). The use of electron diffraction as a legitimate technique in phase identification of pseudomorphic phases in multilayers has been debated.…”

Section: Introductionsupporting

confidence: 77%

“…(1). 6,8 In the thermodynamic framework of Eq. (1), the ⌬G i term was converted from an energy per mole value, common in the literature, to an energy per volume using an average atomic density of the pseudomorphic and bulk equilibrium phases for each of the materials.…”

Section: Introductionmentioning

confidence: 99%

“…(1) needs to be properly extended to account explicitly for E s in measuring the interfacial energy. 6,8 Thus, the location of the data points on the biphase diagram can be used to determine the extent of coherency strains in the system.…”

Section: Introductionmentioning

confidence: 99%

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Erratum: “A comparison of pseudomorphic bcc phase stability in Zr/Nb and Ti/Nb thin film multilayers” [J. Mater. Res. 19, 707 (2004)]

et al. 2004

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A series of Nb-rich Zr/Nb and Ti/Nb multilayers were sputter deposited. Upon a reduction in thickness, a pseudomorphic bcc phase was stabilized in the Zr and Ti layers. X-ray and electron diffraction techniques were used to confirm these phase transformations. The change in phase stability was modeled by the competition between volumetric and interfacial components of the total free energy of a unit bilayer representing the multilayer. An outcome of this model is the ability to plot phase stability diagrams for multilayers, referred to as biphase diagrams, as a function of bilayer thickness and volume fraction. A comparison of the phase stability boundary between hcp/bcc and bcc/bcc for these two systems has shown that the bcc Ti's pseudomorphic phase stabilization is maintained for a much larger layer thickness as compared to Zr. Atom probe compositional profiles of the Ti/Nb multilayers have indicated that the Nb layers interdiffused into the Ti layers thus helping to facilitate the bcc Ti phase stability in the Ti/Nb multilayers.

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Section: Introductionsupporting

confidence: 77%

Section: Introductionmentioning

confidence: 99%

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Erratum: “A comparison of pseudomorphic bcc phase stability in Zr/Nb and Ti/Nb thin film multilayers” [J. Mater. Res. 19, 707 (2004)]

et al. 2004

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“…In fact, interfacial and other thermodynamic effects, which are important in nano-scale systems, can promote the stabilization of metastable phases in thin films. [4,19,20] Further insight into the stabilization of bcc Mg can be derived by studying the evolution of the phonon dispersion with lattice parameter, varying from that corresponding to the fully relaxed bcc Mg 3.571 Å (a 0 , V 0 = 22.769 Å 3 /atom) to bcc Mg with the lattice parameter of Nb 3.324 Å (0.931a 0 , V = 18.363 Å 3 /atom). The phonon dispersion curves of bcc Mg with varied lattice constants were calculated using the PHONON code.…”

Section: Resultsmentioning

confidence: 99%

Stabilization of bcc Mg in Thin Films at Ambient Pressure: Experimental Evidence andab initioCalculations

Junkaew

Ham

Zhang

et al. 2013

Materials Research Letters

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Recent experiments suggest that bcc Mg can be stabilized when grown together with bcc Nb in Mg/Nb multilayer films at ambient conditions. This finding is remarkable as (pure) bcc Mg has only been observed under very high pressures and is in fact (mechanically) unstable under room conditions. Density functional theory calculations were performed to gain insight into the stability of Mg in the bcc structure. Calculations of the thermodynamic, electronic and structural stability of bcc Mg show that this structure is in fact metastable under thin film conditions, when Mg grows epitaxially on bcc Nb, in agreement with experiments.

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“…The first reason is that the strengthening mechanisms occurring in Zr/Nb are not understood. Previous studies on this system focused mostly on structure [50][51][52], superconductivity [53,54] and radiation tolerance [9] of Zr/Nb NMMs, while no consistent correlation between structure and mechanical properties is reported. The second reason is related to the fact that zirconium and zircalloys (Zr-Nb for instance) are widely employed in nuclear industry due to their small capture cross-section for thermal neutrons, their relatively good high-temperature strength and resistance to corrosion [55,56].…”

mentioning

confidence: 99%

Combined size and texture-dependent deformation and strengthening mechanisms in Zr/Nb nano-multilayers

Callisti

Polcar

2017

Acta Materialia

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A combination of transmission electron microscopy analyses and nanomechanical measurements was performed in this study to reveal deformation and strengthening mechanisms occurring in sputtered Zr/Nb nanoscale metallic multilayers (NMMs) with a periodicity (L) in the range 6 -167 nm. Electron diffraction analyses revealed a change in the crystallographic orientation of α-Zr when L ≤ 27 nm, while Nb structure retained the same orientations regardless of L. For L > 60 nm, the strengthening mechanism is well described by the Hall-Petch model, while for 27 < L < 60 nm the refined CLS model comes into picture. A decrease in strength is found for L < 27 nm, which could not be simply explained by considering only misfit and Koehler stresses. For L ≤ 27 nm, plastic strain measured across compressed NMMs revealed a change in the plastic behaviour of α-Zr, which experienced a hard-to-soft transition. At these length scales, the combination of two structural factors were found to affect the strength. These relate to the formation of weaker interfaces which extend the effective distance between strong barriers against dislocation transmission, thus producing a softening effect. 1The second effect relates to the crystallographic orientation change exhibited by α-Zr for L < 27 nm with a consequent change of the dominant slip system. The actual strength at these smaller length scales was effectively quantified by taking these structural aspects into account in the interface barrier strength model.

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Phase stability of bcc Zr in Nb/Zr thin film multilayers

Cited by 55 publications

References 13 publications

Erratum: “A comparison of pseudomorphic bcc phase stability in Zr/Nb and Ti/Nb thin film multilayers” [J. Mater. Res. 19, 707 (2004)]

Erratum: “A comparison of pseudomorphic bcc phase stability in Zr/Nb and Ti/Nb thin film multilayers” [J. Mater. Res. 19, 707 (2004)]

Stabilization of bcc Mg in Thin Films at Ambient Pressure: Experimental Evidence andab initioCalculations

Combined size and texture-dependent deformation and strengthening mechanisms in Zr/Nb nano-multilayers

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