Microstructure and Mechanical Properties of Si(3)N(4)-Fe(3)Si Composites Prepared by Gas-Pressure Sintering

Si(3)N(4)-Fe(3)Si composites were prepared using Fe-Si(3)N(4) as the source of Fe(3)Si by gas-pressure sintering. By adding different amounts of Fe-Si(3)N(4) into the starting powders, Si(3)N(4)-Fe(3)Si composites with various Fe(3)Si phase contents were obtained. The microstructure and mechanical properties of the composites were investigated. With the increase of Fe-Si(3)N(4) contents, the content and particle size of Fe(3)Si both increased. When more than 60 wt. % Fe-Si(3)N(4) were added, the abnormal growth of Fe(3)Si particles occurred and oversized Fe(3)Si particles appeared, leading to non-uniform microstructures and worse mechanical properties of the composites. It has been found that Fe(3)Si particles could toughen the composites through particle pull-out, interface debonding, crack deflection, and particle bridging. Uniform microstructure and improved mechanical properties (flexural strength of 354 MPa and fracture toughness of 8.4 MPa·m(1/2)) can be achieved for FSN40.