The development of deformation substructure and texture has been studied up to large plastic strains in some simple Al base alloys by multiple forging. The experiments involve successive forging strains on near-cube samples along 3 orthogonal axes up to cumulative strains of 3 or more (and temperatures from 20 to 400°C). The alloys include the commercial AA 3103 (Al- 1%Mn) and a laboratory Al-3%Mn-Sc-Zr alloy for the high temperature tests. Some complementary experiments have been carried out on oriented single crystals of Al-0.3%Mn. During 3D cross forging of fcc metals a clear texture composed of three symmetrical components is formed; they are the 3 possible variants of the <110> <110> <100> crystal axes along the 3 forging axes. This macroscopic texture is demonstrated by X-ray pole figure analysis, EBSD mapping and confirmed by crystal plasticity (CP) simulations. At room temperature the alloys (particularly Al-Mn) exhibit significant grain refinement by grain fragmentation leading to "grain sizes" of less than 103m. However, at temperatures ≥ 300°C in the stable Al-3%Mn-Sc-Zr alloy the lattice rotations towards just 3 texture components leads to a high frequency of grain "fusions"; each grain becomes surrounded by 3-5 neighbours of the same orientation so that long interpenetrating chains of the texture components are formed; they are also confirmed by FEG-SEM EBSD and spatially resolved texture simulations. The behaviour of stable (Goss) and unstable (cube) single crystal orientations during the same deformation processing is also investigated and shown to agree with the CP simulations.