Microstructural evolution and mechanical properties of aluminum-graphite composites processed via accumulative roll bonding

In the present work, the aluminum-graphite metal matrix composites were fabricated via accumulative roll bonding (ARB). The graphite powder particles of <50 mu m were introduced into aluminum in three different weight percentages. The effect of graphite on the evolution of microstructure, interface formation, and mechanical properties was studied. The microstructural investigation revealed that the amount of graphite played a vital role. A better particle distribution was observed for 1.25 and 1.5 wt%. However, a further increase in the reinforcement to 2.2 wt% shows longer flaky graphite with comparatively sharing a larger interface area with the matrix aluminum. An FE-SEM/EDS (Field Emission-Scanning electron microscopy/Energy dispersive Spectroscopy) line mapping at the aluminum-graphite interface confirmed an intact sound interface with better adherence properties. The ultimate tensile strength of the composites drastically improved with an increasing number of ARB passes. The FE-SEM taken over the fractured surface of the composite revealed that the ARBed Al-1100 and the composites failed in ductile mode. It was observed that the graphite particle was the primary source of nucleation in the composites. The voids have nucleated at the particle-matrix interface, followed by their growth and coalescence.