Multiphase Forming in Lightweight Composites during SHS Reaction

Abstract

Multiphase microstructures in lightweight composites were formed during self-propagating high temperature synthesis (SHS) reaction under pressure with followed heat treatment. The purpose of multiphase microstructure modelling in composites is an intensification of their functional properties. For this the composites were produced on base of chemical high active superhard refractory advanced ceramic materials such as boron carbide and cubic boron nitride powders. For primary binder phase the metals (aluminum, titanium, iron, chromium, rhenium, nickel) and carbon with different proportions were used. The attrition milling of mechanical activation technique was used in this study. Depending on chemical composition and grain size the ignition temperature (from room temperature up to ~2000 °C) and SHS reaction rates were very different. For phase state investigation the X-ray and field emission scanning electron microscopy techniques were used. Test results show, that these new phases – boron aluminum carbide and ultrafine titanium carbonitride have very large influence on composites microstructure and properties evolution. The hardness of materials was increased meanwhile the dry sliding wear and hydroerosion wear were decreased. The increased concentration of boron carbide and cubic boron nitride safeguarded the good wear resistance properties but materials with this composition were very hard to machinability.