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The Structure and Stress State of Lamellar Interfaces in Two-Phase Titanium Aluminides

  • Fritz Appel (a1), Ulrich Christoph (a1) and Richard Wagner (a1)

Abstract

Titanium aluminide alloys with compositions slightly on the Ti-rich side of stoichiometry consist of the intermetallic phases α2 (Ti3Al) and γ(TiAl). The two phases form a lamellar microstructure with various types of coherent and semicoherent interfaces. The lattice mismatch occurring at the semicoherent interfaces is largely accommodated by networks of interfacial dislocations. Nevertheless, a significant homogeneous straining seems to remain at these interfaces, resulting in long-range residual stresses. The present paper reports an electron microscope study of the correlation between the misfit strain of adjacent lamellae and the atomic structure of the interfaces. The residual coherency stresses were determined by analyzing the curvature of dislocation loops which were emitted from the network of the interfacial dislocations. The estimated stresses are close to the shear stresses applied during macroscopic deformation experiments. The effects of these stresses on the deformation behaviour of the material are discussed.

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The Structure and Stress State of Lamellar Interfaces in Two-Phase Titanium Aluminides

  • Fritz Appel (a1), Ulrich Christoph (a1) and Richard Wagner (a1)

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