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This work focuses on the processing, properties, microstructure, and optimization of squeeze and stir casted samples of scrap aluminum alloy wheel aluminum matrix composites reinforced with alumina. The Taguchi-Grey relational analysis method was used to optimize the stir and casting process parameters, namely, squeeze pressure, squeeze time, die preheating temperature, and stirrer speed. These stir-casted composites were analyzed based on their microstructure, hardness, tensile strength, compression strength, and wear/tribological performance. Adding alumina to an aluminum matrix improved the mechanical and tribological properties. The results showed that out of nine experiments (L1–L9) obtained from Taguchi analysis, experiments L5 and L6 exhibited the best mechanical properties. Microstructural observations revealed different morphologies in the distribution of Al2O3 and porosity in the Al matrix, depending on the process parameters. Finally, the Taguchi-GRA method was used to find the optimized process parameters and was experimentally verified. The optimized sample (M2) showed the lowest porosity (5.29%) and significantly higher ultimate compression strength (433 MPa). However, it exhibited slightly lower hardness and ultimate tensile strength when compared with the L6 and L5 samples, respectively.

Stir casting is one of the most suitable processes for producing Metal Matrix Composites (MMCs) because of its simplicity, proven process, lower cost of production and mass production capability. This paper reviews all the significant attributes of stir casting process such as furnace design, properties of the composites, challenges in the production of the composites as well as the potential research opportunities in the production of composites. We have also provided recommendations for the furnace design, selection of matrix and reinforcement materials as well as process parameters and additives, which makes the review novel. In order to provide a background for any reader interested in the production processes for MMCs, we have also discussed the various approaches in the introductory section briefly. Based on the critical assessment of the literature, especially the mechanical properties of the produced MMCs, a bottom tapping stir casting furnace, preferably with electromagnetic and ultrasonic stirrer along with squeeze attachment is recommended for the production of MMCs.

In the present study, aluminium metal matrix composites (AMCs) were successfully produced through stir-squeeze casting using a novel approach. The feasibility of using car scrap aluminium alloy wheels (SAAWs) as the matrix material and spent alumina catalyst (SAC) from oil refineries as reinforcement material was investigated. For the purpose of comparision, composites were also produced using AlSi7Mg (LM25 grade) aluminium alloy as a matrix and alumina as reinforcement particles through the stir-squeeze casting process. In total, four different combinations of composites (AlSi7Mg + alumina; scrap aluminium alloy + alumina; AlSi7Mg + spent alumina catalyst; scrap aluminium alloy + spent alumina catalyst) were produced and characterized. Microstructural investigations using an optical microscope and a scanning electron microscope (SEM) as well as energy dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD) revealed that in all four composites the reinforcement formed a mixture in the eutectic silicon phase of the matrix alloy. The alumina particles' size and content ratio greatly influenced this mixture's formation and morphology. The composites produced using alumina exhibited smaller pore sizes and lower porosity as compared to the composites produced with a spent alumina catalyst. Superior mechanical properties were also obtained when using alumina as reinforcement, and better mechanical properties can mainly be attributed to the morphology of the reinforcement and silicon eutectic phase mixture. The scrap aluminium alloy + alumina exhibited the lowest porosity (7.3%) and abrasive wear loss (0.11 mg for the finest abrasive), highest hardness (58.5 BHN), and second highest ultimate tensile strength (UTS) (125 MPa) and ultimate compressive strength (UCS) (312 MPa) among the four composites.

In the present work, the influence of stirrer blade design on the dispersion of reinforcement particles in the aluminum metal matrix was studied extensively through experiments and also simulated them using the computational fluid dynamics (CFD) method. The microstructure and mechanical properties of the produced metal matrix composites (MMCs) were studied. The analysis of the microstructure was performed using an optical microscope to visualize the reinforcement distribution and binding within the matrix. Further, field emission scanning electron microscope (FESEM) and X-ray diffraction (XRD) were used to characterize the MMCs. The experimental density was assessed using the Archimedes method, and the theoretical density was determined using the mixture law to determine the percentage of porosity in the MMCs. Hardness, compression, and tensile testing were performed on the produced samples. A three-dimensional computational method was used to predict the flow field of aluminum melt and study the influence of the blade design on the distribution of the reinforcement. Experimental results validated the CFD recommendation on the blade design. The CFD recommendation was based on the structure, power number, and the number of blades, and accordingly, the four-blade flat stirrer (B4) design was the best. The experimental results also corroborated the CFD recommendation with the four-blade flat stirrer design achieving the highest compressive strength (642 MPa), highest hardness (45 HRB), and highest tensile strength (206 MPa) among the five different blade designs investigated.

Aluminium matrix composites (AMCs) find a broader spectrum of applications inconsiderable number of industries globally as AMCs possess excellent mechanical properties at lower mass density. Due to many advantages, researchers continue to find a new generation of materials that offer designers many benefits in converting traditional materials into commercial and industrial materials to use low cost or waste materials as reinforcing phase while producing AMCs. In this research work, Graphene Oxide (GO) is used as a reinforcing phase in the LM6 aluminium matrix, and this paper attempts to lay more emphasis on synthesis and characterization of LM6 matrix and GO particulates and LM6/GO composites as a whole. A modified stir casting process was employed to develop the above composite material. The composite test pieces were subject to physical and mechanical tests, i.e., density, hardness, tensile, and impact. Microanalysis methods such as SEM and XRD analysis were also performed on the composite specimens to analyze the feasibility and suitability of the materials for further research work (friction welding of composites) being pursued by the authors. The results and insights drawn from the comprehensive laboratory analysis demonstrated that the LM6/GO composite could be successfully used as alternative materials replacing metal and alloys. Furthermore, the composite can be easily subject to the welding process resulting in quality welded joints and assemblies.