Heterophase interface

Heterophase Interfaces. In certain cases, sharp heterophase interfaces are able to move in military fashion by the glissile motion of line defects possessing dislocation character. Interfaces of this type occur in martensitic displacive transformations, which are described in Chapter 24. The interface between the parent phase and the newly formed martensitic phase is a semicoherent interface that has no long-range stress field. The array of interfacial dislocations can move in glissile fashion and shuffle atoms across the interface. This advancing interface will transform... 

Available experimental information about the source (or sink) efficiency of heterophase interfaces for fluxes of solute atoms indicates that low efficiencies are often associated with a lack of appropriate ledge defects [2]. 

Strict equality of pressure is required absent capillarity effects if a deforming heterophase interface stores energy during volume transfer, the two phases will have an equilibrium pressure difference. 

Interfaces may also be classified broadly into homophase interfaces and heterophase interfaces. A homophase interface separates two regions of the same phase, whereas a heterophase interface separates two dissimilar phases. Crystal/vapor and crys-tal/liquid interfaces are heterophase interfaces. Crystal/crystal interfaces can be either homophase or heterophase. Examples of crystal/crystal homophase interfaces are illustrated in Figs. B.2, B.4, and B.5. Examples of heterophase crystal/crystal interfaces are shown in Figs. B.6 and B.7. Figure B.6o shows an interface between f.c.c. and h.c.p. crystals where the small mismatch between close-packed lll fcc... 

Figure B.6 (a) Singular heterophase interface between an f.c.c. and h.c.p. structures...

Figure B.7 Construction of a heterophase interface, (a) Reference crystal taken to be...

All sharp crystal/crystal homophase and heterophase interfaces can be classified as coherent, semicoherent, and incoherent. The structural features of these interfaces can be revealed by constructing them using a series of operations which always starts with a reference structure. 

For crystalline-crystalline interfaces we further discriminate between homophase and heterophase interfaces. At a homophase interface, composition and lattice type are identical on both sides, only the relative orientation of the lattices differ. At a heterophase interface two phases with different composition or/and Bravias lattice structure meet. Heterophase interfaces are further classified according to the degree of atomic matching. If the atomic lattice is continuous across the interface, we talk about a fully coherent interface. At a semicoherent interface, the lattices only partially fit. This is compensated for by periodic dislocations. At an incoherent interface there is no matching of lattice structure across the interface. 

Grain boundaries are the most important type of homophase solid-solid interfaces. An example of crystalline heterophase interfaces with high relevance for technological applications are semiconductor heterostructures. 

The modem method for quantifying the goodness of fit between two adjacent grains in a pure poly crystalline substance (homophase interfaces) or in a multiphase solid (heterophase interfaces) counts the number of lattice points (not... 

The terms incommensurate and semi-commensurate are analogous to incoherent and semi-coherent for interfaces - in grain boundaries, heterophase interfaces and epitaxial layers (cf. also Nabarro - with which layered misfit structures have much in common. In extreme cases noncommensurability may arise by mutual rotation (to varying degrees) of component layers with identical component lattices... 

Role of Crain Boundary Structure and Interface Energy at Homophase and Heterophase Interfaces Differences in structure and energy result from the creation of a solid-state interface... 

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