One-Dimensional Antiphase Domain Structures in the Aluminum-Rich Al-Ti Alloys

Abstract

One-dimensional antiphase structures with average domain sizes of non-integral multiples ( M =1.33-1.91) of the basic L l 2 cell, existing in the Al 3- x Ti 1+ x (0< x <1/3), have been studied by high-resolution electron microscopy and X-ray powder diffraction. The mixing mode of M =1 and M =2 domains is revealed and the nature of lattice modulation associated with an antiphase structure is clarified. Ti atoms and Al-rich “statistical” atoms bordering on the antiphase boundaries are displaced away from and towards the boundary, respectively. The amounts of displacement are estimated on the basis of X-ray intensities. It is revealed that the Al 2 Ti appearing in the Al 3- x Ti 1+ x contains a small amount of Ga 2 Zr-type modification in the form of faulted zones within a matrix Ga 2 Hf-type structure. The nature of displacement modulation existing in the stoichiometric Al 2 Ti is also clarified.