Variation in the dislocation structure on lamellar ti₃al/tial interfaces during deformation at different temperatures

Abstract

A Ti-44at.% alloy consisting of Ti₃Al + TiAl lamellar structure was deformed in compression at room temperature, 400[ddot]C. and 800[ddot]C. Studies by transmission electron microscopy were carried out on the nature and distribution of dislocations in the lamellar Ti₃Al/TiAl interfaces before and after deformation. During deformation at room temperature and 400[ddot]C, the interfaces remain straight, on which the interfacial dislocations (IID-1) that are regularly arranged before deformation glide to accommodate the strain gradient across them. The interaction of lattice dislocations with the interfaces disturbs the interfacial dislocations. During deformation at 800[ddot]C, the interfaces on which the interfacial dislocations are rearranged to accommodate the new interfacial misfit become curved. The lattice dislocations injected into the interfaces appear to dissociate. It is suggested that the glide of the interfacial dislocations at lower temperatures as well as the migration of the interfaces at high temperatures play a significant role in improving the ductility of the two-phase alloy.