Abstract
In this study, different volume fractions of silicon-carbide-reinforced AA2024 matrix composites were successfully fabricated using stir-casting (SC) and die-casting (DC) processes. The microstructural difference and physical properties of the composites during the manufacturing process were investigated in detail. The microstructural analysis found that the composite produced by the SC process had some reinforcement clusters and pores; however, defects and clusters significantly decreased after the DC process. In particular, the degree of reinforcement dispersion was quantitatively analyzed and compared before and after the DC process using the dispersion-analysis method. As a result of quantitative evaluation, the degree of dispersion was improved 2.5, 4.6, and 4.0 times with 3 vol.%, 6 vol.%, and 9 vol.% SiC-reinforced composite after the DC process, respectively. The electron backscatter diffraction (EBSD) analysis showed that the grain size of the 9 vol.% SiC-reinforced DC composite (17.67 μm) was 75% smaller than that of the SC composite (68.06 μm). The average tensile strength and hardness of the 9 vol.% SiC-reinforced DC composite were 2 times higher than those of the AA2024 matrix. The superior mechanical properties of the DC-processed composite can be attributed to the increase in dispersivity of the SiC particles and to decreases in defects and grain size during the DC process.
Highlights
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]
SiC has a similar density (3.21 g/cm3) to that of Al (2.81 g/cm3) and has excellent thermal and mechanical properties; SiC is widely used as a reinforcement of metal matrix composites
The manufacturing processes of aluminum matrix composites (AMCs) can be classified into liquid, semi-solid, and solid-state processes [8]
Summary
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]. 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, B4C, Al2O3, and TiB2 [4,5,6,7]. 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. 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. Effects of grain refinement during the solidification process of composites on the composite microstructure were schematically studied
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