Mechanical, microstructural, and textural evaluation of aluminum-MWCNT composites manufactured via accumulative roll bonding at ambient condition

Abstract

In the present study, aluminum-matrix composites reinforced by multi-walled carbon nanotubes (MWCNTs) were manufactured using the accumulative roll bonding (ARB) process. In the first step, MWCNTs were dispersed between two pieces of Al sheets that were then stacked together and rolled. In the second step, the above procedure was repeated for up to 12 cycles without adding MWCNTs. The microstructure and fracture surface of the composites were studied during various ARB cycles using optical microscopy (OM) and scanning electron microscopy (SEM). Also, the mechanical properties of the composites were measured employing tensile and Vickers hardness tests. More uniform dispersion of MWCNTs was found in the microstructure of the aluminum matrix after 12 ARB cycles. With an increase in the number of ARB cycles, the hardness of the composites was enhanced. The results indicated that after 11 cycles, both the elongation and tensile strength improved and strong interfacial bonding formed between MWCNTs and the Al matrix. However, the development of micro-cracks in the composite resulted in a decrease in elongation and tensile strength at the final cycle. SEM investigations of fracture surfaces revealed that the fracture mode of the composites changed from ductile to brittle in the final ARB cycle, while that of monolithic aluminum remained ductile for all ARB cycles. Texture analysis, also confirmed a transition from the initial recrystallized (Cube and Goss) texture to the ideal rolling texture, mainly with Copper and Dillamore components.