A novel two-step method to prepare fine-grained SiC/Al-Mg-Sc-Zr nanocomposite: Processing, microstructure and mechanical properties

Abstract In this study, a novel two-step method consisting of powder metallurgy (PM) and subsequent friction stir processing (FSP) was used for preparing SiC/Al-Mg-Sc-Zr nanocomposites integrating multiple beneficial microstructural factors, including high densification, uniform distribution of SiC nanoparticles, good SiC/Al interfacial bonding and recrystallized fine Al grains. These favorable microstructure factors enables the resultant AMCs to overshadow the classical ductility loss in the particle reinforced AMCs, and achieve good strength-ductility synergy. At room temperature, with increasing the SiC nanoparticle content, the strength of the FSPed samples increases, and the corresponding ductility decreases, but still maintains at a high level. The FSPed AMC with 10 wt% SiC nanoparticles has a highest YS and UTS of about 227 MPa and 329 MPa respectively while maintaining a uniform elongation of nearly 20%. At high temperature (523 K), the strength and ductility variation of the FSPed samples with SiC nanoparticle content is similar to that at room temperature. The YS and UTS of the FSPed AMC with 10 wt% SiC nanoparticles reach about 148 MPa and 166 MPa respectively while the fracture elongation approaches 0.3. The fracture of the FSPed samples shows ductile fracture characteristics at both room and elevated temperatures caused by the microvoid coalescence mechanism. The novel two-step preparation method will assist the development of particle reinforced AMCs with balanced strength and ductility.