Texture transition in friction stir processed Al powder compact

Abstract

Green Al powder compacts of commercial purity with random orientation were subjected to single pass friction stir processing (FSP) with different tool rotational and traverse speeds. The evolution of crystallographic texture obtained from large area electron back scattered diffraction were compared with the bulk texture of the nugget zone characterized using synchrotron diffraction. Evolution of different deformation and recrystallization texture components were discussed. While the grain size distributions were found to be independent of process parameters, the texture components and their strength of the FSPed samples were strongly influenced by the process parameters. Continuous dynamic recrystallization (CDRx) was found to be the primary restoration mechanism for most of the processing conditions leading to a bi-modal misorientation distribution. The possible relations between different texture components and the appearance or suppression of bimodal misorientation distributions were discussed. Restoration mechanism changed to discontinuous dynamic recrystallization (DDRx) with the evolution of cube component at the stir zone along with random misorientation distribution. Dominance of a particular restoration mechanism depends on strain, strain rate and temperature attained during the processing.