Analyse d'une classe de precipites semicoherents fibreux: Cristallographie de l'interface [formula omitted] et champ de deformation

Abstract

High resolution electron microscopic observations of the interface between V 5Si 3 tetragonal fibrous phase and V 3Si cubic matrix are discussed as regards both structure and elastic strain field. The coherence of the large faces of the fiber, due to the parallelism of (001) V 3Si and (011) V 5Si 3 planes, can be analyzed by means of the C lattice formalism suggested by Bonnet and Durand [ Phil. Mag. 32, 997 (1975)]. The crystallographic orientation and width of the large faces can therefore be related to the orientation relationships between the two phases. The occurrence of a dislocation, the Burgers vector of which ±( l 2 ) [001] V 3Si does not belong to the DSC lattice, at only one of the two tips of each face can also be explained. Such an interphase interface model also predicts a translational dislocation array in each face, which accounts for (i) the singularities due to the microsteps and (ii) the fact that the elastic strain field of the fiber is not strictly the same as that of a dipole of translational dislocations, but rather is that of a dipole of type II Somigliana dislocations, as recently proposed by R.B. An analysis is made of the elastic strain field and of the energy stored by unit length, in both cases of isotropic and anisotropic elasticities. Some numerical applications are given which show strong elastic interaction between the large faces of the fiber.