Heterophase dislocations — An approach towards interpreting high temperature grain boundary behavior

Glicksman, M.E.; Vold, C.L.

doi:10.1016/0039-6028(72)90253-1

Cited by 74 publications

(18 citation statements)

References 19 publications

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“…This crude model is su cient to parameterize correctly the temperature dependence of 2 in the classical limit as given in Eq. (2). A more exact theory valid in the quantum limit also, though only in the harmonic approximation, has been presented by Mannheim 16 and has been used by Howard and Nussbaum 17 to analyze the behavior of Fe impurities in various hosts.…”

Section: Discussionmentioning

confidence: 99%

Anomalous temperature behavior of Sn impurities

et al. 1993

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Sn impurities in Pb and Ag hosts have been investigated by Mossbauer effect and in Pb by x-rayabsorption fine-structure (XAFS) studies. The Sn atoms are dissolved up to at least 2 at. %%u o inP ban dup to at least 8 at. % in Ag for the temperature ranges investigated. The concentration limit for Sn-Sn interactions is 1 at. % for Pb and 2 at. % for Ag as determined experimentally by lowering the Sn concentration until no appreciable change occurs in the Mossbauer effect. XAFS measurements verify that the Sn impurities in Pb are dissolved and predominantly at substitutional sites. For both hosts the temperature dependence of the spectral intensities of isolated Sn impurities below a temperature To is as expected for vibrating about a lattice site. Above To the Mossbauer spectral intensity exhibits a greatly increased rate of drop-off with temperature without appreciable broadening. This drop-off is too steep to be explained by ordinary anharmonic effects and can be explained by a liquidlike rapid hopping of the Sn, localized about a lattice site. Higher-entropy-density regions of radii somewhat more than an atomic spacing surround such impurities, and can act as nucleation sites for three-dimensional melting.

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Section: Discussionmentioning

confidence: 99%

Anomalous temperature behavior of Sn impurities

et al. 1993

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“…(1) with respect to w, with V (w) defined by Eq. (2), predicts that, for ∆γ > 0, the liquid layer width vanishes for temperatures less than a "bridging temperature" T b , defined by ∆G(T b ) = −∆γ/δ, and increases smoothly as w(T ) = −δ ln (−∆G(T )δ/∆γ) for T b < T < T m , (3) ultimately diverging as the melting temperature T m is approached from below. For ∆γ < 0, in contrast, boundaries remain completely dry (w(T ) = 0) for all T up to a maximum temperature T * defined by…”

Section: A Sharp-and Diffuse-interface Theoriesmentioning

confidence: 99%

“…The latter can lead to catastrophic material failure as exemplified by hot cracking during high-temperature processing of metallic alloys 1,2 . While there is indirect experimental evidence for the occurrence of grain-boundary premelting in both pure materials 3,4 and alloys 2,5 , it is inherently difficult to image and to measure thermodynamic properties of nanometer-width liquid films. One exception is optical microscopy of colloidal crystals, which has produced striking "atomistic"-scale images of premelted grain boundaries 6 .…”

Section: Introductionmentioning

confidence: 99%

Phase-field crystal study of grain-boundary premelting

2008

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We study the phenomenon of grain-boundary premelting for temperatures below the melting point in the phase-field crystal model of a pure material with hexagonal ordering in two dimensions. We investigate the structures of symmetric tilt boundaries as a function of misorientation θ for two different inclinations and compute in the grand canonical ensemble the "disjoining potential" V (w) that describes the fundamental interaction between crystal-melt interfaces as a function of the premelted layer width w, which is defined here in terms of the excess mass of the grain boundary via a Gibbs construction. The results reveal qualitatively different behaviors for high-angle grain boundaries that are uniformly wetted, with w diverging logarithmically as the melting point is approached from below, and low-angle boundaries that are punctuated by liquid pools surrounding dislocations, separated by solid bridges. The latter persist over a superheated range of temperature. This qualitative difference between high-and low-angle boundaries is reflected in the w-dependence of the disjoining potential that is purely repulsive (V ′ (w) < 0 for all w) for misorientations larger than a critical angle θc, but switches from repulsive at small w to attractive at large w for θ < θc. In the latter case, V (w) has a minimum that corresponds to a premelted boundary of finite width at the melting point. Furthermore, we find that the standard wetting condition γ gb (θc) = 2γ sl gives a much too low estimate of θc when a low-temperature value of the grain boundary energy γ gb is used. In contrast, a reasonable lower-bound estimate can be obtained if γ gb is extrapolated to the melting point, taking into account both the elastic softening of the material at high homologous temperature and local melting around dislocations.

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“…This interaction is relevant for understanding grain coalescence and grain-boundary premelting phenomena. The latter has been extensively studied experimentally [16,17,18] and theoretically using lattice models [19,20], atomistic molecular dynamics or Monte Carlo simulations [21,22,23] (with earlier references therein), multi-phasefield models [10,11], frame-invariant phase-field models [12,13], and phase-field crystal models [24,25]. Even though grain boundary premelting is not fully understood, there is emerging concensus that it originates fundamentally from a repulsive interaction between crystalmelt interfaces for high-energy grain-boundaries, which is directly relevant for the present study.…”

Section: Introductionmentioning

confidence: 99%

Multi-phase-field analysis of short-range forces between diffuse interfaces

Wang

Spatschek

2010

Phys. Rev. E

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We characterize both analytically and numerically short-range forces between spatially diffuse interfaces in multi-phase-field models of polycrystalline materials. During late-stage solidification, crystal-melt interfaces may attract or repel each other depending on the degree of misorientation between impinging grains, temperature, composition, and stress. To characterize this interaction, we map the multi-phase-field equations for stationary interfaces to a multi-dimensional classical mechanical scattering problem. From the solution of this problem, we derive asymptotic forms for short-range forces between interfaces for distances larger than the interface thickness. The results show that forces are always attractive for traditional models where each phase-field represents the phase fraction of a given grain. Those predictions are validated by numerical computations of forces for all distances. Based on insights from the scattering problem, we propose a new multi-phase-field formulation that can describe both attractive and repulsive forces in real systems. This model is then used to investigate the influence of solute addition and a uniaxial stress perpendicular to the interface. Solute addition leads to bistability of different interfacial equilibrium states, with the temperature range of bistability increasing with strength of partitioning. Stress in turn, is shown to be equivalent to a temperature change through a standard Clausius-Clapeyron relation. The implications of those results for understanding grain boundary premelting are discussed.

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Heterophase dislocations — An approach towards interpreting high temperature grain boundary behavior

Cited by 74 publications

References 19 publications

Anomalous temperature behavior of Sn impurities

Anomalous temperature behavior of Sn impurities

Phase-field crystal study of grain-boundary premelting

Multi-phase-field analysis of short-range forces between diffuse interfaces

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