Coherency stresses and interface-related deformation phenomena in two-phase titanium aluminides

Phase equilibria and transformations in near-equiatomic titanium aluminides lead to the formation of a lamellar structure comprising of the intermetallic phases alpha(2)(Ti3Al) and gamma(TiAl). Due to differences in lattice parameters and crystal structure, coherency stresses and mismatch structures occur at various types of semicoherent interfaces present in the material. The present paper reports an electron microscope study of the atomic structure of the interfaces. The residual coherency stresses present at the interfaces were determined by analysing the curvature of dislocation loops which were emitted from the network of interfacial dislocations. The implication of these stresses on the deformation behaviour of the material will be discussed. (C) 1999 Elsevier Science Ltd. All rights reserved.