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Aluminum alloy-based (Al7075) surface hybrid nanocomposite (SHNC) was fabricated by incorporating a reinforcement mixture of nano-aluminum oxide, micro-boron carbide, and graphite by utilizing friction stir processing (FSP). The graphite particle ratio was varied in the reinforcement mixture and its influence on the tribological properties of Al7075 SHNC was studied. In the metal matrix surface composite, the scanning electron microscope (SEM) and field emission SEM (FESEM) depict a homogeneity in the distribution of reinforcements. The nanocomposite’s wear behavior under dry sliding environments was investigated by adopting a central composite design (CCD) at three levels by response surface methodology (RSM). The designed experiments were executed in pin-on-disc (POD) apparatus, with load, sliding distance, and graphite ratio as input variables. The influence of applied factors and their interaction with the response were determined using an analysis of variance. To predict the wear characteristics, a mathematical model is formulated. Load is discovered to be a significant factor influencing the wear rate and friction coefficient. In addition, an increase in graphite% results in a lower wear rate for the given quantity of load and sliding distance. SEM image shows a severe wear pattern for higher load and lower graphite content. The optimum combination of the parameter obtained from multi-response optimization was load 10[Formula: see text]N, sliding distance 503.86[Formula: see text]m, and 14.99% graphite for reducing the wear rate and friction coefficient by applying the desirability function approach.

Aluminium alloy surface hybrid nanocomposite, reinforced with boron carbide (B4C), aluminium oxide (Al2O3), and Graphite (Gr) at different combination mixtures by weight ratio have been fabricated on Al7075-T6 aluminium plate by employing friction stir processing (FSP). The mixtures of definite proportions were packed in an array of blind holes 2.5mm in diameter and 3mm deep which are 6mm apart from each other. FSP was done with processing factors of 750 rpm revolving speed, 20mm/min feed, and tool angle of 3o. The prepared hybrid composites were sectioned for microstructure, macrostructure, wear, and hardness evaluation. In the metal matrix surface composite, the scanning electron microscope (SEM) and field emission scanning electron microscope (FESEM) depict the homogeneity in the distribution of reinforcement elements, microstructure, and wear behaviour. Under dry sliding conditions, the nanocomposite's wear behaviour was investigated by adopting a central composite design (CCD) at 3 levels in response surface methodology (RSM) for optimization. The wear characteristics are analyzed using pin on disc apparatus. The wear property of the nanocomposites with distinct reinforcement ratios was evaluated. Higher hardness values (maximum of 191Hv) were found in hybrid nanocomposite samples than in the plain FSPed samples (149Hv) without reinforcement. It is evident, that the wear loss depends on the relative weight ratio of B4C and Al2O3 with a constant amount of graphite and the minimum wear loss of 2.9421mm3 is obtained from composite with 30B4C+60Al2O3+10Gr reinforcement ratio than the wear loss of 8.2292mm3 obtained from plain FSPed composite. The optimal combination of parameters, Al2O3 60%, load 20N, and velocity 1 m/s was identified from RSM. The hybrid nanocomposite having a reinforcement mixture of 30B4C+60Al2O3+10Gr exhibits a significant wear resistance than other combination ratios. This is endorsed by the enhancement in binding strength of the matrix and the pinning effect of hard reinforcements, which act against the applied shear force.

Aluminium hybrid composites are identified as new generation of metal matrix composites for its good strength to weight ratio and good corrosion resistance properties. However their mechanical properties and tribological properties are still lower than that of commonly applied materials. Hence it is necessary to improve the surface qualities of aluminium matrix and makes it suitable for engineering applications. Friction stir processing (FSP) is an emerging technique which can be used to make surface composites. While FSP of different alloys has been considerably reviewed, surface reinforcement by hybrid nanocomposites on aluminium matrix have not been wholesomely reviewed. The present review offers a comprehensive understanding of friction stir processed aluminium matrix hybrid nanocomposites. The available literature provide the details about the effect of process parameters, reinforcement particles, microstructural evolution during the fabrication of aluminium matrix hybrid nanosurface composites. Few research gaps in fabrication of aluminium matrix surface composites has been revealed in this review such as micro alloying with low melting point metals, defect free composites and interrelationship between process parameters.