Mechanical performance of extruded Ti–46Al–5Nb–1W titanium aluminide

Abstract

Titanium aluminide alloys offer considerable promise for use in high temperature applications, such as gas turbines. In this study an extruded Ti–46Al–5Nb–1W alloy has been examined, in terms of its tensile and creep behaviour. A reasonably fine and uniform microstructure was found in this bar product. This gave excellent properties, with tensile strengths up to ∼950 MPa at room temperature, along with 1% elongation. These properties were accompanied by a very good creep behaviour, with low primary strains at the lower stresses and very low secondary creep rates. Comparison of the creep properties of this titanium aluminide alloy with other similar compositions and some typical nickel alloys shows that it is significantly superior to first generation titanium aluminides but also nickel alloys, such as IN718 and Udimet 720Li. However, the strain controlled fatigue performance of the titanium aluminide alloy was significantly poorer than these same wrought nickel alloys.

Keywords:

• Titanium aluminide
• Creep
• Fatigue

The authors would like to thank UK Ministry of Defence Applied Research Programme and the Department of Trade and Industry Aerospace Research Programme for funding this work and Mr R. Savage, Mr M. Squibb and Mr M. Sumner for assistance with the tensile and creep testing. In addition, thanks are due to Plansee (Tyrol, Austria) and Rolls-Royce (London, UK) for the supply of the material.