Slip transfer between lamellae in fully lamellar TiAl alloys

TEM observations have shown that not only does slip transfer take place from one gamma lamella to adjacent gamma lamellae, but slip transfer also takes place at gamma/alpha-2 interfaces during deformation of lamellar TiAl alloys. The various possible slip transfer mechanisms between gamma/alpha-2 lamellae and gamma/gamma lamellae have been analysed. The results show that unit dislocations and twinning in the gamma lamellae can be transferred into the alpha-2 lamellae by actuating 1/6[11 (2) over bar 6] or 1/6[11 (2) over bar 0] dislocations. It is also shown that the gamma/alpha-2 interface is less transparent than the gamma/gamma because the CRSS of the slip systems in the alpha-2 phase is high and the geometry makes the reactions concerning twinning dislocations in the gamma phase more difficult. The significance of these mechanisms is briefly discussed in terms of the limited ductility of lamellar TiAl alloys. (C) 1999 Elsevier Science Ltd. All rights reserved.