PREPARATION OF ALUMINA-CHROMIUM COMPOSITES BY REACTIVE HOT-PRESSING AL+CR2O3 BASED POWDERS

Chromium-Alumina based composites have been obtained by reactive sinte ring under load and vacuum of various powder blends. The starting mixt ures have been prepared from commercially available aluminium metal, c hromium and aluminium oxides, and a thermally unstable titanium compou nd respectively. Differential thermal analysis (DTA) and differential calorimetry (DSC) as well as X-ray diffraction were used to identify c hemical transformations taking place within the system. Microstructure changes were observed via scanning electron microscopy (SEM) with an energy dispersive spectroscopy system (EDS). Chemical reactions in rel evant binary subsystems have been investigated qualitatively in order to understand the course of events in the more complex quaternary mixt ures. The possibilities of forming intermetallic phases in both the AI -Ti and Cr-Ti systems and of dissolving some Cr2O3 into the product Al 2O3 phase have been considered. The influence of such parameters as th ermal schedule and initial aluminium content on those side reactions a nd the resulting microstructures was investigated.