Strain ageing in γ(TiAl)-based and α2(Ti3Al) titanium aluminides

Deformation of α2(Ti3Al) and γ(TiAl)-based alloys between 150 and 550 °C is characterized by negative strain-rate sensitivity and strain ageing effects. These phenomena are usually associated with dislocation locking according to the Portevin-LeChatelier effect. The dislocation pinning processes associated with these phenomena were studied by static strain ageing experiments. The dislocation locking is generally more significant for off-stoichiometric compositions, when compared with stoichiometric α2 or γ alloys leading to the conclusion that antisite atoms are involved in the dislocation locking mechanism. The main features of this mechanism are described in the present paper together with its effects on the deformation behaviour.