Influence of the change of the deformation path on deformation banding in Cu-8%Al alloy single crystals
Abstract
The textural and microstructural effects of cross rolling of fcc metals with low stacking fault energy have been studied by local orientation measurements in the SEM equipped with field emission gun (FEG) and by X-ray pole figure measurements. The analysis is focused on shear bands and deformation bands development by plane strain compression in copper-8%wt. aluminium alloy single crystals with twinned C{112}< 111 > and non twinned CR{112}< 110 > orientations as well as in twinned CRP{112}< 110 > samples after changing of the deformation path as a result of 90 degrees ND vertical bar vertical bar < 112 > rotation. It has been found that important transitions of the deformation textures are correlated with deformation banding. In C{112} < 111 >-oriented samples and in those after the change of the deformation path (i.e. in {112}< 110 > pre-deformed as {112}< 111 > the high resolution SEMFEG orientation maps allowed investigation of the way in which unstable behaviour of twin-matrix layers leads to the "brass"-type shear bands and formation of the deformation bands. Within well-developed shear bands the dominance of crystal lattice rotation about one of the < 112 > poles was observed. This is correlated with the operation of one of the two, initially equally active co-planar slip systems of {111} < 110 >-type. As a consequence, the rotation of twinned areas within shear bands is observed. This ultimately leads to formation of texture components near the B{110}< 112 >-S{123}< 634 > fibre. In non-twinned CR{112}< 110 > orientation from the beginning stages of deformation, a strong tendency to decomposition as a result of < 112 > rotation is also clearly observed. This leads to another type of deformation bands resembling the transition ones. From crystallographic point of view the tendency to form two nearly complementary positions of B{110}< 112 > orientation is observed.