Microstructural and mechanical characterization of co-pressed, co-sintered ceramic bi-materials

In this study alumina (Al2O3), magnesium aluminate spinel (MgAl2O4) powders were uniaxially co-pressed, thus green compact of bi-materials were produced. Besides production of bi materials, alumina and spinel powders were also uniaxially pressed and mono materials produced by this way. The produced monomaterials and bi-materials green compacts were sintered at 1600 ºC for 4 hours soaking or without soaking and dense materials were tried to produce. For each part of bi materials's indentation hardness and elastic modulus were tested by indentation technique with the applying loads of 300, 400, 424 and 450 mN. Maximum and minimum indentation depth and elastic recovery rate of bi-materials were measured for each region and the obtained results were compared with literature and evaluated. Indentation fracture toughness of alumina and spinel parts of bi-materials were measured and the results were discussed with each other and also compared with theoretical results. Archimedes density of mono-materials were measured and discussed with each other. Vickers hardness of mono-materials were tested and discussed with each other. After sintering, microstructure of mono-materials and bi-materials were investigated under optical microscope and scanning electron microscope. Average grain size of mono-materials (alumina and spinel) were measured from scanning electron microscope and dicussed. Thickness of interface layer formation between alumina and spinel were discussed depending on kind of material and duration of sintering.