Interfacial microstructure of dual-scale SiCp/A356 composites investigated by in situ TEM tensile testing

Abstract

Silicon carbide particle (SiCp) reinforced Al matrix (SiCp/Al) composites have broad application prospects in high-end equipment manufacturing fields such as aerospace and automotive nowadays. The volume fraction and size of SiCp reinforcement play a decisive role in the physical and mechanical properties of the composites. Herein, we have prepared the dual-scale SiCp/Al composites through the powder metallurgy method. The interfacial microstructure and crystal orientation relationship at the interface was observed and analyzed. And then we have investigated the fracture behavior of the SiCp/Al interface by employing the in situ TEM tensile experiment. The results of the in situ TEM tensile testing show that when there exists a MgAl2O4 interface layer with thickness of 100 nm in the prepared SiC/Al composite, the microcracks are formd preferentially at the MgAl2O4/Al. And the interface bonding strength of the SiC/MgAl2O4 is higher than that of MgAl2O4/Al. Moreover, the microcracks are formed firstly at the sharp corners of micron SiCp and the interface. With the increaing load, the microcracks propagate along the micron SiCp and the interface. With the further increase of the load, connections and mergers will occur between the formed microcracks, which will eventually lead to the breakage of the specimen. Besides, the addition of the dual-scale SiCp can improve the yield strength of the A356 obviously.