On the microstructure and texture of intermetallics in Al/Mg/Al multi-layer composite fabricated by Accumulative Roll Bonding

The microstructure and texture of the intermetallics in Al/Mg/Al multi-layer composite fabricated by Accumulative Roll Bonding (ARB) at 400 C up to 6 cycles were investigated using Electron BackScatter Diffraction (EBSD) and Synchrotron X-ray Diffraction (SXRD). EBSD and SXRD analysis have shown that ARB processing leads to the formation of Al3Mg2 and Mg17Al12 intermetallics soon after the second ARB cycle with a global thickness of 12 (N = 2) to 22 mu m (N = 6). The polycrystalline intermetallics plates growth was columnar and normal to the bonding interface. A constitutional liquefaction region was depicted ahead of the plates with an unusual rugged migration front. The Al3Mg2 and Mg17Al12 intermetallic compounds which formed after 2 ARB cycles have approximately the same average grain size (1.0 mu m) at this cycle. After 4 ARB cycles, the grain refinement of Al3Mg2 is more than 4 times higher than in Mg17Al12. The average grain size of Al3Mg2 and Mg17Al12 reach 0.2 and 0.9 mu m, respectively. After 6 cycles of ARB, the average grain size of both Al3Mg2 and Mg17Al12 increased to 1.5 mu m and 2.8 mu m, respectively. The dislocation density obeyed a rho(Al3Mg2) > rho(AZ31) > rho(Al 1050) similar to rho(Mg17Al12) hierarchy after N = 4 and 6 ARB cycles and the Al3Mg2 was shown to store more dislocations. Through the ARB processing, a usual strong basal (0002) texture was depicted in AZ31 layers and a weak rolling texture was shown in Al 1050 layers with a dominant Rotated Cube (001) 110 > component that vanished after upon increasing ARB cycles. The Al3Mg2 and Mg17Al12 intermetallics were characterized by a random texture.