A novel in situ composite structure in TiAl alloys

Phase decomposition and ordering reactions in β/B2-phase containing TiAl alloys were utilized to establish a novel, previously unreported, type of in situ composite. The characteristic constituents of this composite are laths with a modulated substructure that are comprised of several stable and metastable phases. The modulation occurs at the nanometer-scale and thus leads to a significant refinement of the material. Microstructural control by conventional thermomechanical processing results in a structurally and chemically very homogeneous material with appreciable mechanical properties. The physical metallurgy of this novel type of alloy has been assessed by high-resolution transmission electron microscopy and mechanical testing.