Preparation of alumina-chromium composites by reactive hot-pressing A1 + Cr₂O₃ based powders

Abstract
Chromium-Alumina based composites have been obtained by reactive sintering under load and vacuum of various powder blends. The starting mixtures have been prepared from commercially available aluminium metal, chromium and aluminium oxides, and a thermally unstable titanium compound respectively. Differential thermal analysis (DTA) and differential calorimetry (DSC) as well as X-ray diffraction were used to identify chemical 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 relevant binary subsystems have been investigated qualitatively in order to understand the course of events in the more complex quaternary mixtures. The possibilities of forming intermetallic phases in both the Al-Ti and Cr-Ti systems and of dissolving some Cr₂O₃ into the product Al₂O₃ phase have been considered. The influence of such parameters as thermal schedule and initial aluminium content on those side reactions and the resulting microstructures was investigated.