Accumulative roll-bonding: first experience with a twin-roll cast AA8006 alloy

An ultra-fine grained (UFG) material was prepared from a twin-roll cast (TRC) Al-Fe-Mn-Si (AA8006) sheet using accumulative roll-bonding (ARB) process. After initial failures to achieve good sheet bonding, five cycles of ARB at 200 deg. C were successfully performed. Scanning electron microscopy (Electron Backscatter Diffraction) and transmission electron microscopy (TEM) were used for the characterization of subgrain and grain structures of ARB processed samples. The strength of ARB sheets was evaluated by microhardness measurements. Very fine grain structure (0.4-0.8 μm) with large disorientation was observed after two cycles of ARB. In two samples, areas with extremely fine grains 0.1-0.3 μm in diameter were found. The hardness of the alloy increased from 28 to 60 HV1 after the first two cycles, but during subsequent ARB processing it rose only very slightly