On the use of Somigliana dislocations to describe some interfacial defects

Abstract

The concept of a Somigliana dislocation (SD) has been used in calculations of the elastic fields of interfacial defects. It has been found useful to define rectangular interfaces in terms of two different types of SD, the elastic fields of which have been determined by using the theory of a continuous distribution of dislocation loops and previous results obtained by Kroupa (1965) for the elastic field of a semi-infinite dislocation dipole. SDs of these two types have been used to describe the elastic fields associated with cubic or prismatic fibrous coherent precipitates. Each face of such a precipitate acts like an SD, so that the elastic field of the whole precipitate can be calculated from the elastic interactions of either six (for cubic precipitates) or four (for fibrous precipitates) SDs. The procedures appears to be widely applicable. Examples are presented of its application to the consideration of non-uniform sliding along phase boundaries in a lamellar eutectic, to the determination of elastic fields associated with twin boundaries of complex structures and to the discussion of the elastic field of a simple tilt boundary.