Atom Probe Field Ion Microscopy of Poly Synthetically Twinned Titanium Aluminide

Abstract

Abstract Two phase γ-based TiAl alloys are attractive for structural applications at high temperatures because they possess good elevated-temperature mechanical properties, low density, and good creep and oxidation resistance. The microstructures of these alloys consist of plates of the near equiatomic γ phase (L10-ordered structure) and the Ti3Al α2 phase (D019-ordered structure). It is of great interest to study the details of the lamellar α2+γ microstructure because the interface stability is the key to providing a usable high temperature material. Polysynthetically twinned (PST) TiAl crystals have been developed in order to systematically study the lamellar microstructure. These PST materials contain no high angle grain boundaries and have an single set of aligned lamellae of a α2 and γ phases, as shown in Fig. 1. Therefore, PST samples facilitate the study of the dependence of mechanical properties on lamellar structure by providing a known, consistent set of aligned lamellae.