Effect of elastic anisotropy on the dissociation widths of superdislocations in TiAl

The dissociation widths of the 〈101̄] and 1/2〈112̄] superdislocations in TiAl have been calculated by the elasticity theory that the elastic interaction energies and stacking fault energies acting on the partial dislocations are equal. The results show that the dissociation widths of the screw 〈101̄] and 1/2〈112̄] superdislocations in anisotropic condition are smaller than that of isotropic condition, but the dissociation widths of the edge 〈101̄] and 1/2〈112̄] superdislocations in anisotropic condition are larger than or equal to that of isotropic condition. The equilibrium separations of the superlattice intrinsic stacking fault (SISF) formed by the two-fold 〈101̄] and 1/2〈112̄] superdislocation dissociations are nearly the same with each other in the elastic isotropy condition but are different in the elastic anisotropy condition. The stacking fault energy of SISF in a high-Nb TiAl alloy, which was evaluated to be about 45-55 mJ/m² from the 〈101̄] superdislocation dissociation and to be about 62-69 mJ/m² from the 1/2〈112̄] superdislocation dissociation using the isotropic calculation, is determined to be about 80±5 mJ/m² from both the 〈101̄] and 1/2〈112̄] superdislocation dissociations using the anisotropic calculation.