Long-Period Antiphase Domain Structures of Al-Ti Alloys near Composition Al₃Ti

Abstract

Superstructures of Al-Ti alloys in the composition range from Al3Ti to Al2Ti were studied by electron diffraction. It was shown that the Al24Ti8 which has been reported to be a low temperature modification of the Al3Ti phase has a long-period one-dimensional antiphase domain structure (1d-APS) with average domain size M=8/6, where M is measured in unit cell length of the fundamental lattice. In addition, the 1d-APS's with M=1.60–1.91 were found in the specimens containing 26.5 to 32.5 at.% Ti and it was suggested that the 1d-APS's with M=1.67–1.91 correspond to the high temperature phase Al5Ti2 (or Al11Ti5).

Phase equilibria investigations on the aluminum-rich part of the binary system Ti-Al

“…According to the phase diagram proposed by Loiseau et al, [19] these long period structures are only stable above 1000 ЊC. Miida et al [34] reported one-dimensional antiphase domain structures for alloys containing 67.5 to 73.5 at. pct Al heat treated at 1200 ЊC.…”

Trialuminide intermetallic alloys for elevated temperature applications—overview

“…The existence of the phases TidAl. and TizAl5 in A13xTi~.~ alloys has also been reported as the result of other detailed electron microscope investigations [29,30,34] but these works have not provided an indication of the origins of these phases.…”

“…For the same composition range, Miida et al [27,34] and Loiseau et al [30,35], working primarily with electron diffraction, identified a series of ld-APS (long period structures), which were distinguished in terms of composition and structure by the average domain size M and the axial ratio c/a of the fundamental sub-cell of the structure. Miida et al [27] suggested that the ld-APS found in an alloy containing 31 at.% Ti, after quenching from 1473 K, had M=1.79 and corresponded to TisAln.…”

A Study of the Kinetics of Phase Transformations in Nb-Ti-Al Alloys

“…The I4/amd space group of the 0 phase is, however, the same as the TiAl 2 intermetallic compound [27,[60][61][62][63][64]. In the binary Ti-Al system, the TiAl 2 phase can take on two different crystal structures h-TiAl, and r-TiAl 2 depending on temperature [27] (see Figure 3.18).…”