ON THE INFLUENCE OF ORIENTATION PINNING ON GROWTH SELECTION OF RECRYSTALLIZATION

With the help of techniques for local orientation determination it has been proved that the recrystallisation textures of Al-alloys evolve b y a preferred formation of some orientations at characteristic nucleat ion sites and a subsequent growth select;on of distinct orientations o ut of this spectrum of nucleus orientations. As an alternative to the standard explanation of a favoured growth of grains with a special ori entation relationship to the deformed matrix (e.g. 40 degrees [111]), recently the concept of ''orientation pinning'' has been proposed, whi ch considers that the growth selection is determined by special orient ation relationships being disfavoured (low-angle and twin grain bounda ries). The present paper reviews the two rivalling theories of oriente d nucleation and oriented growth to explain recrystallisation textures and addresses the new approach of orientation pinning. New EBSD-resul ts on commercial purity Al which substantiate a growth selection of th e exact cube-orientation out of the nucleus spectrum available in the cube-bands and the R-orientation out of the nucleus spectrum of the gr ain boundaries are presented. A semi-quantitative model to simulate th e effect of orientation pinning on the evolution of recrystallisation textures is introduced. The results are discussed in view of growth se lection and the 40 degrees [111] orientation relationship. (C) 1998 Ac ta Metallurgica Inc.