Properties and microstructure of TiAl-based alloys

A range of TiAl-based alloys has been plasma melted and subsequently either isothermally forged, extruded or atomised and HIPped. The microstructure and properties of these alloys have been determined and some aspects of the relation between processing route, alloy composition and properties will be discussed. It is clear that room temperature strengths between 1000 and 300 Mpa can be obtained for different compositions and processing routes, but room temperature elongation is generally the least attractive of the properties with values of 2% being typical of the best observed. The relation between room temperature strengths and creep response is not straightforward and some typical results will be reported. On the basis of these observations and earlier work on the influence of high temperature exposure on the structure of lamellar and duplex alloys, it is suggested that there may be significant advantages of using processing routes which generate a fine grained duplex structure.