Deformation behavior and high-temperature stability of unidirectionally solidified, twin phase TiAl

Abstract

Ti-50.8% Al has been cast using unidirectional solidification to produce specimens with a highly directional structure. Each specimen consisted of the intermetallic phases, TiAl and Ti 3 Al. Both phases existed as single crystal lamellae which were parallel to each other throughout the specimen and aligned along specific crystallographic orientations. Mechanical properties were assessed by deforming specimens such that slip occurred in different directions relative to the lamellae. High-temperature stability was assessed by heating for various times and examining the microstructure. Deformation revealed a highly anisotropic structure since ductility depended upon the principal direction of slip. Poor slip, occurring in a direction through the lamellae, was attributed to the Ti 3 Al phase where cracking initiated. Heating at 1200 °C resulted in recrystallization of the TiAl phase. The recrystallization started at the ends of the specimens as a result of residual mechanical damage, before spreading along individual lamellae into the bulk.

Micro-image analysis in the diffusion-bonded zone of Fe3Al/Q235 carbon steel dissimilar materials

“…Fe 3 Al is a newly developed intermetallic, which has unique electronic and magnetic properties as well as excellent resistance to corrosion and oxidization by the addition of alloying elements such as Cr, B, Ce and Zr (Mckameey et al 1991;Fair and Wood 1994). But the additional alloying elements can easily cause the second phase precipitation in Fe 3 Al intermetallic compound.…”