Solid-State Processing Route, Mechanical Behaviour, and Oxidation Resistance of TiAl Alloys

Figure 5

Midsection of the binary Ti-Al phase diagram and representative microstructures obtained through heat treatments within the - and -phase field. Note that the left half of the microstructural image represents a light-optical microscope (OM) image, whereas the right half is an SEM image taken in BSE mode, i.e., -TiAl appears dark, whereas -Ti₃Al shows a light contrast. Heat treatments: little above the eutectoid temperature () near gamma (NG) microstructure; between and -transus temperature duplex (DM) microstructure. The volume fraction of lamellar grains depends on the heat treatment temperature relative to and ; just below nearly lamellar (NL) microstructure. The designation NL stands for a NL microstructure exhibiting a defined volume fraction of globular -grains, above FL microstructure (adopted from [16]).