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

Abstract

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 µm (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 µm) 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 µm, respectively. After 6 cycles of ARB, the average grain size of both Al₃Mg₂ and Mg₁₇Al₁₂ increased to 1.5 µm and 2.8 µm, respectively. The dislocation density obeyed a ρ_Al3Mg2 > ρ_AZ31 > ρ_{Al 1050} ∼ ρ_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.

Keywords: Accumulative roll bonding; Al1050/AZ31/Al1050; Dislocation density; Intermetallic compounds; Microstructure; Texture.