Effect of texture components on plastic anisotropy and formability of aluminium alloy sheets

Abstract

Plastic anisotropy of the typical preferred orientations appearing in textured aluminium alloy sheets has been analyzed on the basis of the continuum mechanics of textured polycrystals (CMTP) anisotropic yield function proposed by Jonas et al. In addition, in-plane plastic anisotropy of differently textured aluminium alloy sheets has been predicted and compared with the experimental results. Three components of {011}〈112〉, {123}〈634〉 and {112}〈111〉, which are the main conponents of retained texture, display the short and thick yield loci in the RD–TD orthogonal coordinates and slender ones in the coordinates rotated by 45° form the rolling direction in the sheet plane. Corresponding to the yield loci, each of the retained texture gives a peak of R value above unity in the neighborhood of 45° from the rolling direction and R values that equal to or less than unity at 0 and 90°. In contrast with the reatined texture components, a typical recrystallization texture, {001}〈100〉 cube component reveals the same yield locus as the von Mises' criterion in the RD–TD coordinates and circle-like one in the 45–135° coordinates. Cube texture gives the minimum R value of zero at 45° and the maximum one equal to unity at 0 and 90°. Either the reatined texture or cube texture causes large plastic anisotropy in the sheet plane and is unfavourable to deep drawing. However, if the retained texture components and cube texture are appropriately mixed, they can counter the in-plane anisotropy of each other and realize in-plane plastic isotropy, leading to the improvement of drawability. Both the analytical and experimental results indicate that cube texture has a beneficial effect on the drawability of sheets, rather than being an unfavorable component.