Abstract:A macro-structure-toughened SiC particle reinforced LD2 aluminum alloy matrix (SiCp-LD2/LD2) composite was designed and fabricated based on considering the main factors which result in low room temperature fracture toughness of conventional metal matrix composites. Its room temperature fracture toughness was tested using three-point bending samples with sing1e edge notches. Compared with conventional SiCp/LD2 composites fabricated by stirring casting in case of same particle size and similar reinforcement volume fraction, this composite has a higher room temperature fracture toughness KQ. It shows strong resistance to crack propagating. The crack in it can propagate stably for a long time on the maximum load, therefore abrupt fracture occurring in most conventional composites can be avoided. Bending fractography (SEM) shows that the fracture mechanism of this material is different from SiCp/LD2 composite and the deformation of the unreinforced LD2 matrix and the SiCp-LD2/LD2 interface debonding are the main toughening mechanisms of this composite。debonding are the main toughening mechanisms of this composite. 

Key words:  metal matrix composite; fractures; crack propagation; interface