Effects of particle/matrix interfaces on the mechanical properties for SiCp or YAl2p reinforced Mg-Li composites

YAl2p or SiCP reinforced Mg-14Li-3Al (LA143) matrix composites were prepared by stir-casting. The composites were subjected to fracture toughness and tensile tests. The particle/matrix interfaces were investigated by nanoindentation combined with scanning electron microscopy (SEM). The effects of the particle/matrix interfaces on the mechanical properties of the composites were discussed through a unit cell model with a transition interface layer. The results show that a transition interface layer with smoother hardness and modulus gradient is developed in the YAl2/LA143 composite. Both the fracture toughness and ductility for the YAl2/LA143 composite are higher than those for the SiC/LA143 composite. The failure behavior is determined by particle breakage with little interfacial breakage for the YAl2/LA143 composite, while being due to interfacial breakage for the SiC/LA143 composite. The superiority of the mechanical properties for the YAl2/LA143 composite may result from the failure behavior of particle breakage, which are correlated to the better physical compatibility between the YAl2 intermetallics and LA143 matrix.