Intermetallic titanium aluminides offer an attractive combination of low density and good oxidation and ignition resistance with unique mechanical properties. These involve high strength and elastic stiffness with excellent high temperature retention. Thus, they are one of the few classes of emerging materials that have the potential to be used in demanding high‐temperature structural applications whenever specific strength and stiffness are of major concern. However, in order to effectively replace the heavier nickel‐base superalloys currently in use, titanium aluminides must combine a wide range of mechanical property capabilities. Advanced alloy designs are tailored for strength, toughness, creep resistance, and environmental stability. These concerns are addressed in the present paper through global commentary on the physical metallurgy and associated processing technologies of γ‐TiAl‐base alloys. Particular emphasis is paid on recent developments of TiAl alloys with enhanced high‐temperature capability.

No abstract

No abstract

No abstract

No abstract

No abstract

A two-phase titanium aluminide alloy was systematically doped with carbon to improve its high temperature strength. Solid solutions and precipitates of carbon were formed by different thermal treatments. A fine dispersion of perovskite precipitates was found to be very effective for improving the high temperature strength and creep resistance of the material. The strengthening mechanisms were characterized by flow stresses and activation parameters. The investigations were accompanied by electron microscope observation of the defect structure which was generated during deformation. Special attention was paid on the interaction mechanisms of perfect and twinning dislocations with the carbide precipitates.

The deformation behaviour of two-phase titanium aluminides was investigated in the intermediate temperature interval 450–750 K where the Portevin-LeChatelier effect occurs. The effect has been studied by static strain ageing experiments. A wide range of alloy compositions was investigated to identify the relevant defect species. Accordingly, dislocation pinning occurs with fast kinetics and is characterized by a relatively small activation energy of 0.7 eV, which is not consistent with a conventional diffusion process. Furthermore, the strain ageing phenomena are most pronounced in Ti-rich alloys. This gives rise to the speculation that antisite defects are involved in the pinning process. The implications of the ageing processes on the deformation behaviour of two-phase titanium aluminide alloys will be discussed.