EVOLUTIONS OF GRAIN ORIENTATION AND DISLOCATION BOUNDARY IN AA1050 ALUMINUM ALLOY DURING COLD ROLLING FROM LOW TO MEDIUM STRAINS

The dislocation boundary structure evolution in AA1050 aluminum alloy during cold rolling from low to medium strains was investigated using electron channeling contrast(ECC) imaging and the electron backscattered diffraction(EBSD) techniques.The results show that the grains are subdivided into a typical cell-block structure and there is a strong correlation between deformation microstructure and grain orientation.Based on the characterizations of grain subdivision and dislocation boundary structure,grains can be classified into three types:Type A—grains containing two sets of geometrically necessary boundaries(GNBs),Type B—grains containing one set of GNBs,and Type C—grains consisting of large dislocation cells structure.Most of grains with Copper,Brass and Goss orientations have Type A microstructure;grains with S orientation have Type B microstructure, grains with Cube orientation have Type C microstructure.The alignment of the extended dislocation boundaries depends strongly on the grain orientation.In most grains the boundaries have inclination angles of±(30°—40°) to rolling direction(HD).and are approximately parallel to the traces of the most active {111} slip planes as identified by a Schmid factor analysis.