Fabrication of Yttria stabilized zirconia-silicon carbide composites with high strength and high toughness by spark plasma sintering of mechanically milled powders

Abstract

Lightweight ultra-fine grained (<1 μm size) YSZ-SiC composites, with a combination of high hardness, high flexural strength and high fracture toughness, were successfully prepared by mechanical milling followed by spark plasma sintering. The YSZ-SiC composites exhibited high hardness (13-20 GPa), which is very similar to the hardness of SiC. The YSZ-SiC composites also exhibited high flexural strength (as high as 1142 MPa) and high fracture toughness (up to approximately 8 MPa-m1/2), which are similar to those of the fine-grained YSZ. Such a combination of mechanical properties was attributed to the fine microstructure with a distinct feature consisting of almost continuous network of YSZ phase around SiC particles. It has been demonstrated that a combination of these unique microstructural characteristics was very effective in suppressing the initiation of cracks and governing the path of their subsequent growth during fracture, leading to excellent combination of mechanical properties.