Investigation and simulation of hot forming of alumina based materials

Abstract

Hot forming of a MgO-doped alumina and of a alumina-based nanocomposite has been carried out at 1400°C under vacuum. The forming consisted of discs of the materials being punched between graphite parts into hemispheres. The loading data are presented along with a simulation of these data. The MgO-doped alumina disc broke before completion of the test, whereas the alumina based nanocomposite disc was formed into a hemisphere with reduced damage. Calculated loading data fitted monitored loading data satisfactorily. Microstructural investigations were performed on the nanocomposite hemisphere. The microstructural damage consisted of reduced cavitation which occurred essentially in a shallow region of the outer surface of the hemisphere. The reduced damage observed on the nanocomposite microstructure must be associated with the fineness of the microstructure and the reduced alumina grain growth in this material. Considering the severity of this forming process in terms of deformation, this test illustrates very well the superplasticity of the nanocomposite material. These observations confirmed results gathered from compressive testing.