Dislocation Boundary Structure from Low to Medium Strain of Cold Rolling AA3104 Aluminum Alloy

The evolution of the dislocation boundary structure during the cold rolling of the AA3104 aluminum alloy has been investigated using electron channeling contrast (ECC) imaging and electron backscattered diffraction (EBSD) techniques. The results show that there is a strong correlation between the dislocation boundary structure and the grain orientation. No strong effect of strain level or second-phase particles on the structure-orientation correlation is found. Based on these observations, the microstructures can be classified into one of 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 a structure of large dislocation cells. Grains with a type A microstructure have orientations near the copper, brass, and Goss orientations; grains with a type B microstructure are primarily near the S orientation; and grains with a type C microstructure have orientations near the cube orientation. The alignment of the extended dislocation boundaries depends strongly on the grain orientation. In most grains, the boundaries are parallel to the traces of the most active {111} slip planes, as identified by a Schmid factor analysis.