A literature review on Al-Si alloy matrix based in situ Al-Mg 2 Si FG-composites: Synthesis,microstructure features,and mechanical characteristics

The current study examined a comprehensive review of the literature on functionally graded composites, particularly Al-Mg₂Si in situ metal matrix composites. Functionally graded Al-Si-Mg₂Si in situ metal matrix composites are potential materials for meeting a variety of property demands in various components of automotive engines. The in situ formed intermetallic compound Mg₂Si in Al-Si matrix exhibits a high melting temperature, low density, high hardness, a low thermal expansion coefficient, and a reasonably high elastic modulus. Due to all of aforementioned characteristics, Mg₂Si is an attractive form of reinforcement that can be created in situ using a simple melt reaction approach. However, the coarse size of primary Mg₂Si reinforcement in cast composites is a demerit which reduces the strength and ductility of the ultimate composite. Hence several researches have been attempted to refine the primary Mg₂Si particles as well as to change the morphology of the eutectic structure. Apart from the monolithic in situ cast composites, attempts have been made to develop functionally graded (FG) composites in which the volume% of segregation of reinforcements are intentionally varied from one surface to another. These types of FG composites are economically developed by centrifugal casting technique in which Mg₂Si reinforcements are segregated to inner the surface due to lower relative density with respect to the molten Al matrix. This type of graded microstructure results in higher strength, hardness and wears resistance at the inner surface of the tubular products. The as-cast microstructure and properties are significantly improved by solution treatment and aging. In the last, some of the most recent manufacturing techniques for FG-composites are addressed, along with their benefits, drawbacks, and applications. In general, all cutting-edge and detailed surveys of the present state of knowledge are included in this article.