Microstructure and mechanical properties of Al matrix nanocomposites reinforced by different amounts of CNT and SiCW

This study aims to investigate the effect of carbon nanotube (CNT) and silicon carbide whisker (SiCW) reinforcements on mechanical properties of aluminum matrix composites. In this study, different amounts of CNT (0-5 wt%) and silicon carbide whiskers (0-5 wt%) were used for fabricating aluminum matrix composite samples. To distribute the reinforcements, aluminum powder and the reinforcements were mixed in a planetary ball mill with rotating speed of 120 rpm at different times (0.5, 1, and 2 h). The results showed that the optimum milling time is 1 h. Then samples were hot pressed under the pressure of 500 MPa at different times and temperatures. Scanning electron microscopy images of the samples fabricated by hot pressing showed that the optimum hot-pressing temperature is 550 degrees C. The effect of the type and the amount of reinforcement and hot-press time on density, hardness, yield strength, and compressive strength of the samples were also investigated. The results showed that, with decreasing the CNTs content (up to 0.5 wt %), the compression strength reaches a maximum (290 MPa), but with increasing CNTs content more than (0.5 wt%), it is degraded due to the agglomeration. In contrast, with increasing the SiCW content up to 3 wt%, the mechanical properties increases proportionally. The compression strength of the composite containing 3 wt% SiCW increased by 33.9% compared with the pure aluminum. Economically, it is preferred to use reinforcements that improve the properties at lower contents. As a result, CNT is a superior reinforcement in comparison with silicon carbide whiskers.