On the hierarchy of planar fault energies in TiAl

Abstract

The combination of computational and experimental weak-beam transmission electron microscopy (WB-TEM) dislocation imaging is suitable to distinguish between the dislocation core models proposed for the [011]-super dislocation in TiAl on the basis of the energy hierarchies (H1) and (H2). The preliminary occupational results presented here suggest that the hierarchy of planar fault energies in Ti-54at.%Al is E{sub CSF}>E{sub APB}>E{sub SISF}{approx}E{sub SESF}, (H2). The value of the antiphase boundary (APB) energy for TiAl is likely to be larger than E{sub APB}>250 mJm-2, whereas the superlattice intrinsic stacking fault (SISF) energy appears to be E{sub SISF} = 140 mJm{sup {minus}2} which is comparable to the superlattice extrinsic stacking fault (SESF) energy, E{sub SESF} = 142 mJm{sup {minus}2}. CSF stands for complex stacking fault.