The in-situ synthesis and strengthening mechanism of the multi-scale SiC particles in Al-Si-C alloys

Highlights: • The synthesis mechanism of multi-scale SiC_p in Al-28Si melts was investigated. • The in-situ SiC nanoparticles were firstly synthesized in large quantity. • The synergistic strengthening effect of multi-scale SiC particles was discussed. Multi-scale reinforcement combining micro-sized and nano-sized has attracted great interests with the properties expected to exceed the respective single one because of their synergistic effect. In the present work, the multi-scale SiC particles were in-situ synthesized using the liquid-solid reaction method in Al-28Si melts. The in-situ SiC nanoparticles were firstly synthesized in large quantity and distributed uniformly in the aluminum matrix. The SiC particles formed through the gradual-reaction mechanism have small sizes, which range from 0.4 μm (sub-micro scale) to 2.2 μm (micro scale). More interestingly, the synthesis of SiC nanoparticles is achieved by the direct reaction mechanism through the [C] and [Si] in the Al melts which average size is less than 50 nm. Furthermore, it has been found that the Rockwell hardness, the wear resistance and the thermal expansion coefficient (CTE) of the fabricated SiC_p reinforced composites are significantly improved due to the synergistic strengthening effect by multi-scale SiC particles.