The spreading of deformation in a lamellar Ti-47Al-1Cr-0.2at%Si alloy deformed under compression was studied at 25 and 600C. This microstructure was largely dominated by twin-related variants which were separated by either twin interfaces or thin α2 slabs. The alloy deforms at both temperatures by ordinary dislocations and twins. Deformation in a particular γ variant and its adjacent twin-related variant involved the same kind of glide system, either ordinary dislocations or twins. This property was found to be true for all twin-related lamellae. The occurrence of this correlated glide was explained by the introduction of the notion of pilot and driven orientations. The lamellar orientation in which the operating glide system was activated on the basis of Schmid factor considerations was termed the pilot orientation. It imposes its deformation system on to the twin-related lamella, called the driven orientation, whose deformation might not involve the slip system most favored by the applied stress.

The Activation and the Spreading of Deformation in a Fully Lamellar Ti-47Al-1Cr-0.2at%Si Alloy. J.B.Singh, G.Molénat, M.Sundararaman, S.Banerjee, G.Saada, P.Veyssière, A.Couret: Philosophical Magazine, 2006, 86[16], 2429-50