Effect of high pressure torsion on interfaces and mechanical properties of SiC/Al composite

Powder mixture of pure Al and oxidized SiC was consolidated into 10 wt% SiCP/Al composite by high pressure torsion at 473 K with the torsion numbers of 1, 4 and 8. The SiC-Al interfaces evolutions and Al matrix were studied by transmission electron microscope (TEM), energy dispersive spectroscopy (EDS), the valence of elements was detected by X-ray photoelectron spectroscopy (XPS). The results show three different interfaces in the HPT-processed samples, namely the SiO2-Al interface, SiO2-Al2O3 interface and SiC-Al2O3 interface. Elements inter-diffusion occurred at both of these three interfaces, but the solid-state atomic reaction 3SiO2+Al -> Al2O3+3Si only can be characteristic at the original SiO2-Al interface. High-density dislocation and Al2O3 layer increase the element diffusion distance. After 8 turns HPT process, the SiC particles remained in the fracture of 8 turns HPT sample is the least. The relative density and mechanical properties (Vickers hardness, tensile strength and elongation) are the best compared to 1 and 4 turns sample which imply the desirable interface bonding between 1, 4 and 8 HPT turns.