Development of Aluminum Alloy Sheet with Excellent Formability through Texture Control by Asymmetric rolling

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Large shear strain exceeding 4.0 was successfully introduced in 1050 aluminum sheet by 2-pass differential roll speed rolling. The shear texture of which main components were {111}<110>, {112}<110> and {001}<110> prevailed throughout the thickness, and conventional rolling texture such as {112}<11> or {123}<634> orientation was not observed in any part of thickness. The intensity of shear component increased with shear strain. The rolling direction of the second pass exerts a little effect on the deformation texture. After recrystallization annealing, shear texture components are retained.The r-value of 1050 aluminum sheet was not affected by roll speed ratio, however Δr slightly decrease with increasing roll speed ratio. The pass schedule of 2-pass differential speed rolling slightly had an influence on r-value which becomes maximum in 2-pass equal reduction rolling. The r-value of the sheet rolled by 2-pass reverse shear rolling, in which the sheet was turned 180 degree around its ND … More axis before second pass rolling, was slightly higher than that of 2-pass unidirectional shear rolling, in which the sheet was turned 180 degree around its TD axis before second pass.The r-value of 5182 aluminum alloy sheet increased with roll speed ratio, and was 0.9 at the roll speed ratio of 1.8. The sheet rolled by conventional (symmetric) rolling without lubrication attained the r-value of 0.85 that is higher than of commercial 5182 alloy sheet. Even in conventional rolling, large shear strain is introduced near the surface of rolled sheet when rolling is conducted under high friction condition. Near the surface of conventionally rolled sheet, shear texture of which <111> axis is just parallel to the ND axis develops, whereas <111> axis slightly inclines towards rolling direction in differential speed rolling. The small difference between r-values of conventionally rolled sheet and asymmetrically rolled sheet is probably due to this difference of <111> axis direction. However the these r-values are higher than that of the sheet rolled by conventional rolling with lubrication. The effect and usefulness of shear strain on the r-value was confirmed.The recrystallized grain size decreased with increasing roll speed ratio. The smallest grain size attained in the present study was 4μm. The strength also inereased with roll speed ratio without loss of ductility.We have succeeded in improving press formability and strength of aluminum alloy sheet by differential speed rolling, bay which shear deformation can be introduced throughout the thickness of rolled sheet. It is proved that the differential speed rolling is promising process for improving physical and mechanical properties of rolled sheet by microstructure and texture control. This process can be applied not only for aluminum alloy but also for other metallic materials. Less