Microstructure and Tensile Properties of Ultrafine Grained Pure Al Sheets Produced by Accumulative Roll Bonding

Abstract

Usually the heat treatment in the cyclic ARB passes is indispensable to reduce work-hardening effects and improve interface bonding quality. The possibility of accelerating grain refinement of aluminum sheets with a dimension of 300 mm×50 mm×1 mm is investigated during the ARB process at room temperature, in which the samples are rotated by 180 degree around normal plane axis perpendicular to the rolling plane between the adjacent cycles. By means of optical microscopy and transmission electron microscopy, it shows that the bonding interfaces can not obviously observed after five cycles, and grains are refined to be ~0.5 μm. Tensile tests show the ARB samples exhibit strain hardening behavior after yielding without a sudden fracture even up to seven cycles of ARB. The softening behavior and enhanced ductility was explained by dynamic recovery, the recrystallization process and even abnormal large grains.