Mechanical Properties of α-SiC and Correlation to SiC/Si Interface at Nanoscale from Reaction Bonded SiC/Si Composites (RBSC)

Reaction bonded SiC/Si (RBSC) composites composed of α-SiC, β-SiC and crystalline-Si phases manufactured at high temperature are widely used in different applications due to their outstanding performances in extreme service conditions. Although the macroscopic mechanical properties of these materials have been extensively explored, there are questions remaining unanswered such as the local material behavior compared to the SiC/Si interface, mechanistic responses in nanoscale and the micro- to nanoscale mechanical properties of major individual components after experiencing the reaction bonding process. In this study, nanoscale specimens were prepared by utilizing Ga focused ion beam (FIB) and an in-situ tensile testing platform was established with a testing stage accommodated inside a field emission scanning electron microscope (FE-SEM). Maximum tensile strength, elastic modulus and Weibull modulus of the nanoscale α-SiC specimens were measured to be 22.9 GPa, 321 GPa and 4.1, respectively. The maximum failure strength was found to be as high as 80% of the theoretical fracture strength. The fracture was found to originate at the side of the specimen surface and appeared to propagate in a brittle manner. The overlap of tensile strength ranges of α-SiC and SiC/Si interface suggests the consistency with an observation of mixed fracture modes in RBSC.