Diffusion of Au in the Intermetallic Compound Ti3Al

Abstract

The Au diffusion in the Ti 3 Al compound was investigated at six compositions from 25 to 35 at. pct Al by using the diffusion couples (Ti-X at. pct Al/Ti-X at. pct Al-2 at. pct Au; X = 25,27, 29, 31, 32, and 35) at 1273 to 1423 K. The diffusion coefficients of Au in Ti 3 Al D Ti 3 Al Au are relatively close to those of Ti. The D Ti 3 Al Au s slightly increase with Al concentration within the same order of magnitude. The activation energies of Au diffusion, Q Ti 3 Al Au s; evaluated from the Arrhenius plots were relatively close to those of Ti diffusion, Q Ti 3 Al Ti s; rather than those of Al diffusion, Q Ti 3 Al Al s; therefore, it was suggested that Au atoms diffuse by the sublattice diffusion mechanism in which Au atoms substitute for Ti sites preferentially in Ti 3 Al and diffuse by vacancy mechanism on Ti sublattice. The influence of the D0 19 ordered structure (hcp base) of Ti 3 Al on diffusion of Au and other elements is discussed by comparing the diffusivities in Ti 3 Al and a-Ti.

Effects of substitutional impurity Au and Si atoms on antiphase boundary energies in Ti3Al: A first principles study

“…APB-free) crystal. Site preferences of Au and Si atoms in APB-free Ti 3 Al were deduced from diffusion studies in which the activation energies of Au and Si diffusion are found to be close to those of Ti and Al diffusion, respectively, in Ti 3 Al, [14,15]. The preference of the Au atom for the Ti site was also deduced from the ternary Al-Au-Ti phase diagram in which the Ti 3 Al single-phase region is elongated along a line for constant Al concentration [29].…”

“…The authors have measured the diffusivities of Au [14], Si [15] and O atoms [16], which are the major possible impurities in Ti 3 Al as conductive diffusion barriers. However, all the measured diffusivities were bulk diffusivities in coarse-grained crystals or single crystals, and therefore the diffusivities in Ti 3 Al containing a high density of lattice defects still remain unknown.…”

“…This tendency is contradictory to the prediction that Au atoms preferably substitute for Ti site in APB-free Ti 3 Al. This prediction was based on the experimental facts: (i) 2 -Ti 3 Al single phase region in the Au-Ti-Al ternary phase diagram is elongated along the line of constant Al-concentration [29]; (ii) the diffusivity of an Au atom in Ti 3 Al is close to that of a Ti atom rather than that of an Al atom [14]. This prediction is also supported by a recent first principles study which indicated that the formation energy Philosophical Magazine 3929 of an APB-free Ti 3 Al containing Au atom is smaller in the case where Au atoms are on Ti sites than in the case where they are on Al sites [31].…”

Spin vortices, skyrmions and the Kosterlitz-Thouless transition in the two-dimensional antiferromagnet

“…The 2D nonlinear sigma model has an instanton solution [16,17,18,19] (being interpreted as skyrmion or meron [20,21]) which describes an excitation of spin-vortex type. Quantum fluctuations of instantons were computed and found to be reduced to the study of the Coulomb gas [22,23,24].…”