Study on microstructural evolution of SiCox/Al-4.2Cu-4.0Mg composites during aging process

For SiCox/Al-4.2Cu-4.0 Mg composites, the addition of Mg content tends to have a significant effect on the interface microstructure and aging precipitation behavior, which in turn affects the mechanical properties of the composites. In this study, we investigated the precipitation behavior, interfacial microstructure evolution, and mechanical property changes of SiCox/Al-4.2Cu-4.0 Mg composites. The results showed that the hardness of SiCox/Al-4.2Cu-4.0 Mg composites increased by 54 %, 61 %, and 48 % at aging temperatures of 170 °C, 190 °C and 210 °C, respectively. The precipitation phase in the matrix is the S′ phase with a size of 70–105 nm, and the precipitation sequence in the composites was GPB zone → S″ phase → S′ phase → S + θ phase when aging temperature was 190 °C. During over-aging process, Ostwald ripening caused the formation of Al 2 CuMg and Al 2 Cu particle larger than 120 nm in the matrix. When the aging treatment time was 18 h, a new interface appeared in the interface reaction layer, and the composition of the interfacial layer changed from MgAl 2 O 4 phase to Al 2 CuMg phase and MgAl 2 O 4 phase. This study can provide suggestions for regulating the composition of interface reaction layer, aging precipitation behavior of aluminum matrix and mechanical properties of aluminum matrix composites reinforced with medium volume fraction SiC particles.