Investigation on Microstructure and Fatigue Characteristics of Spray-Formed SiCp/Al–20Si Composite

The microstructures, high-cycle fatigue properties, fatigue crack growth and fatigue facture surfaces of spray-formed composite and its matrix alloy were investigated, respectively. The results show that the high-cycle fatigue properties of SiCp/Al–20Si composites are superior, as SiC particles improve the mechanical properties of composite. The fracture of Si and the interfacial debonding including both Al/Si and Al/SiC were the principle mechanisms in the fatigue fracture of composite materials. Detailed quantitative analyses indicates that the extensive SiC particle cracking induces a high level of fatigue crack closure, which effectively reduces the crack growth rate, resulting in superior fatigue crack propagation properties for a given ΔK, i.e. lower crack growth rate and higher intrinsic threshold stress intensity factor as compared to the matrix alloy. Crack deflections around SiC particles and particle cracking are the principle mechanisms of interaction between SiC particles and crack tip.