Microstructures And Mechanical Properties Of SiCp/AZ91 Magnesium Matrix Composites Fabricated By Squeeze Casting

SiCp/AZ91 magnesium matrix composites with three particle sizes of 5μm, 20μm and 50μm were fabricated by squeeze casting technique, the volume fraction of them was 50% in all cases. The microstructures of the materials were examined by means of scanning electron microscope (SEM) and transmission electron microscope (TEM). The room temperature and high temperature mechanical properties of the composites were studied, and the fracture behavior of the composite was investigated by in-situ SEM observation. The thermal expansion behavior was examined by dilatometer (DIL) and the damping capacity was evaluated by dynamic mechanical analysis (DMA).The results showed that, a lot of fine discrete interfacial reaction products were observed at the SiCp-AZ91 interface, and the interfacial reaction product is MgO confirmed by the ring diffraction pattern. These interfacial reaction products are mainly from the reaction between the binder and the melted magnesium. There exists a definite orientation relationship between MgO and SiC particle, the strength of combination is comparatively high. So, modest interfacial reaction is beneficial to interfacial bonding between SiCp and Mg matrix, resulting in an improvement of the mechanical properties.Compared with the matrix alloy, the mechanical properties (ambient temperature and high temperature tensile strength) and physical properties (thermal expansion behavior and damping capacity) have a comprehensive performance.Among three kinds of composites, as the size of SiCp decreases, the composites have higher mechanical properties, lower coefficient of thermal expansion and worse damping capacity. The higher mechanical properties is due to that the tensile properties of SiCp/AZ91 composite with small particles are controlled by the properties of matrix alloy and the strength of the SiCp-AZ91 interface, but which with large particles are controlled by the fracture of the particles. The lower coefficient of thermal expansion is attributed to the much more interface areas and the larger constrain effect of the SiC particles on the matrix. The worse damping capacity is considered to the less moveable...