Parts | Days | Selection | Search | Downloads | Help

M: Metallphysik

M 23: Intermetallische Phasen I

M 23.3: Fachvortrag

Wednesday, March 28, 2001, 15:45–16:00, S5.3

⁴⁴Ti Interphase Boundary Diffusion in Two-Phase α₂/γ TiAl — •S. Divinski¹, F. Hisker¹, A. Bartels², and Chr. Herzig¹ — ¹Institut für Materialphysik, Universität Münster, Wilhelm-Klemm-Straße 10, 48149 Münster — ²Technische Universität Hamburg-Harburg, Eißendorfer Str. 42, 21071 Hamburg

Two-phase TiAl alloys consisting of alternating layers of α ₂-Ti₃Al and twinned γ -TiAl phases are known to present promising materials for high-temperature structural applications. In such industrial materials the density of interphase boundaries (IB) is very large, since typically the interlamellar spacing is about 5 µm. Thus, the diffusion study of IB diffusion is very important for elucidating the self-diffusion effect on e.g. creep behavior in these alloys. ⁴⁴Ti interface self-diffusion in the two-phase PST TiAl with 48 at. % Al was measured within the temperature interval from 1050 to 1200 K by conventional radiotracer method. The linear tails of the penetration profiles in coordinates lnc vs. y^6/5 can be followed over 3 to 4 decades (c is the layer concentration and y the depth). The calculated IB diffusivities P turned out to be in line with the Ti grain boundary (GB) diffusivity in Al-rich α₂-Ti₃Al and are smaller by about two orders of magnitude than Ti GB diffusion in γ-TiAl, which both were previously investigated in our group. Such a behavior correlates with the specific atomistic structure of the interphase boundaries, which are atomically flat and correspond to the {111} planes in the tetragonal L1₀ structure of γ -TiAl and to the (0001) basal planes in the hexagonal D0₁₉ structure of α ₂-Ti₃Al.