## 1 Introduction  
In recent decades, because of their properties of high strength-to-weight ratio and corrosion resistance, aluminum alloys have attracted attention as promising materials in many industries [1; 2; 3]. However, these alloys have application limits due to their absolute mechanical properties, which are lower than those of other structural materials (steel, titanium, etc.). To overcome this drawback, many studies have been performed to fabricate aluminum matrix composites (AMCs) with advanced mechanical properties by adding hard ceramic particulates such as SiC, B\({}_{4}\)C, Al\({}_{2}\)O\({}_{3}\), and TiB\({}_{2}\)[4; 5; 6; 7]. Among many ceramic reinforcements, SiC has a similar density (3.21 g/cm\({}^{3}\)) to that of Al (2.81 g/cm\({}^{3}\)) and has excellent thermal and mechanical properties; thus, SiC is widely used as a reinforcement of metal matrix composites. The manufacturing processes of AMCs can be classified into liquid, semi-solid, and solid-state processes [8]. The powder metallurgy process, which is a solid-state method, has the advantage of fabricating high-volume fraction composites; however, its drawbacksinclude a complex process and high cost [9]. On the other hand, liquid-state processes are known to be inexpensive and easy, with excellent productivity. However, liquid metal processes such as stir-casting (SC) make it difficult to ensure the uniform dispersion of ceramic particles in the matrix due to poor wettability and density differences [10; 11; 12; 13; 14; 15]. [PERSON] et al. [16] investigated the mechanical properties of composites fabricated by SC. They found that fractures occurred at reinforcement agglomeration areas. They also found that it was very difficult to control the various defects (pores, clusters) during the SC process because there are many variables such as the shape and size of the particles, the design and position of the stirrer, the stirring speed, the operation and holding time, the mold temperature, the solidification speed, etc. [17; 18; 19]. Hence, to improve the quality of composites, it is necessary to conduct a subsequent process such as rolling, extrusion, or die-casting. Die-casting (DC), a widely used metal-forming process, has many advantages compared to other methods, such as dimensional accuracy, near net shape, and high productivity. However, because of the difficulty of the process, few studies have been conducted on the microstructure and mechanical properties of Al matrix composites produced by DC. There have been attempts to fabricate AMCs using DC processes with control of the process parameters. [PERSON] et al. [20] fabricated bulk Al\({}_{2}\)O\({}_{3}\)/SiC/Al6061 composite by DC; they focused on the effects of optimum process parameters such as casting pressure, die design, and thickness on the composite properties. [PERSON] et al. [21] investigated the effect of fluid shear, vacuum, and intensification pressure for particle distribution and pores formation. High pressure caused an increase in fluid velocity, which generated fluid shear force during mold filling. This may have contributed to the uniform particle distribution and reduction of the size of the pores. [PERSON] et al. [22] fabricated high-performance TiB\({}_{2}\)-reinforced Al-alloy composites via a super-vacuum-assisted die-casting process. The average grain size of \(\alpha\)-Al in the matrix decreased by about 60% after the addition of TiB\({}_{2}\) nanoparticles; the grain refinement led to an improvement of the mechanical properties. The important factors in the DC composite process are the porosity, solidification rate, and, especially, dispersibility. However, there has been little research into the details of the dispersion mechanism or quantitative analyses of particles and their effects on the microstructure and mechanical properties of AMCs. In this study, AA2024 matrix composites with 0, 3, 6, and 9 vol.% SiC were fabricated using both SC and DC processes.