MECHANICAL-THERMAL SYNTHESIS OF AL2O3-CR COMPOSITE POWDERS

Three different approaches have been investigated to synthesize alumin a-chromium composites by displacement reactions between aluminium and chromia. The reactions have been performed either by pure mechanosynth esis or pure thermal ignition or also by a combined mechanical and the rmal activation process. Differential thermal analysis, dilatometry an d high temperature X-ray diffraction have been used to show the variou s reaction mechanisms and chemical transformations High-energy milling of the powder modifies the reactivity of the system. A partial pre-mi lling treatment not only reduces the reaction temperature but can also induce a different reaction path. It has been shown that an appropria te mechanical-thermal treatment lends to the synthesis of an alumina-c hromia composite by a pure solid-state process: intermediate reaction stages exhibit little if any liquid phases.