The effect of local composition on defect structure in a near-γ-TiAl alloy with duplex microstructure

Abstract

The chemical compositions and lattice parameters have been measured locally in primary equiaxed γ grains and in lamellar γ laths of a near-γ-TiA1 alloy with duplex microstructure. The measurements were performed by means of energydispersive X-ray spectroscopy and convergent-beam electron diffraction respectively. It was found that the local compositions as well as the lattice parameters are different in primary and lamellar γ grains. In lamellar γ laths the concentration of Al is lower and the Nb concentration is higher than in the primary γ grains, while the concentrations of Ti and Mn are the same in both kinds of grain. The tetragonality in the γ laths was found to be lower than in the primary grains. The differences in chemical composition are suggested to be mainly responsible for the different deformation substructures in primary and lamellar γ grains reported in the literature while the differences in lattice parameters play only a minor role.