Microstructural investigation of an Al–Cu lamellar nanocomposite produced by accumulative roll bonding process under the heat treatment condition: an analytical, experimental, and finite element study

Abstract

The microstructural evolution of a heat treated and accumulative roll bonded (ARBed) Al–Cu composite was studied using different metallurgical methods. Alumina particles were also added to the matrix of the composite to observe the effect of particles on the formation of the intermetallic compounds (IMCs) during heat treatment. Before heating, it was seen that Cu layers fractured in the Al matrix during the ARB process and the mean grain size of the composite reached less than 500 nm after the sixth ARB cycle. Optical microscopy (OM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) investigations were conducted on the Al–Cu composite to monitor microstructural changes before and after the heat treatment process. It was observed that diffusion of the Al and Cu atoms occurred during heat treatment of the composite. Moreover, SEM investigations revealed that only two kinds of IMCs namely AlCu and Al4Cu9 thrived through the matrix of the composites. Gibbs's free energy for the components was then evaluated and confirmed the formation of the IMCs between the metallic layers. A finite element method (FEM) was also employed to determine Cu layer thickness changes and fracture behavior of the Al–Cu ARBed materials. It was seen that induced pressure by the rollers made considerable changes in the Cu thickness. Also, the first fracture mode (mode Ⅰ) was determined to be more destructive as compared to the second fracture mode (mode ⅠⅠ) for the heat treated materials.

Keywords

• Al–Cu composite
• Accumulative roll bonding
• Alumina
• Diffusion
• Heat treatment
• Intermetallic compounds