Effects of strain accumulation and annealing on interfacial microstructure and grain structure (Mg and Al3Mg2 layers) of Al/Cu/Mg multilayered composite fabricated by ARB process

Abstract

In this research, Al/Cu/Mg multilayered composites were produced by the accumulative roll bonding (ARB) process and then annealed at different temperatures and times. Microstructural studies showed that with increasing temperature and annealing time in the zero cycle samples, the thickness of the intermetallic compounds (Al3Mg2 and Al12Mg17) increased. Also, optical microscopy (OM) images displayed that the Al3Mg2 growth rate was higher than Al12Mg17. The effect of accumulative strain in various annealing conditions on the thickness of the intermetallic compounds is very low. Its effect is more accelerated to the nucleation of the compounds. Plus, the growth mechanism of the intermetallic layer of Al/Mg was determined to be controlled by diffusion and reaction. The activation energy of Al3Mg2 and Al12Mg17 were calculated to be 73 and 143 Kj.mol−1, respectively. Evaluation of the grain structure of magnesium layers showed that the grains were equiaxed and strain-free for magnesium at zero cycle and different heat treatment conditions. Besides, shear bands formed by the shear strain concentration enhanced the nucleation of magnesium grains around them in the annealing process and diminished the size of magnesium grains compared to the farther regions. Furthermore, the layer of Al3Mg2 intermetallic compound with equiaxed column structure formed after annealing at different temperatures and times as well as various cycles of ARB.

Keywords

• Multilayered composite
• Annealing
• Intermetallic compound
• Kinetics of growth
• Strain accumulation
• Grain structure