Mechanical behavior of cordierite and cordierite–mullite materials evaluated by indentation techniques

Commercially available cordierite and mullite powders were used to obtain cordierite and composite materials with mullite content up to 65 wt.% by attrition milling, uniaxial pressing and sintering. Cordierite powders were the coarse, medium and fine single granulometric fractions and the binary mixtures of them with 30, 50 and 70 wt.% of the smaller component. Mullite powder employed in composites was the 7 h-attrition milled one. The Vickers hardness (HV) and fracture toughness (KIC) were measured by Vickers indentation techniques. The Knoop hardness (HK) and Youngʹs modulus (EK) were estimated by Knoop indentation method. Fracture surfaces of sintered materials were analyzed using a scanning electron microscope (SEM). The indentation load to determinate the fracture parameters was previously determined. The influence of the porosity, increasing mullite and glassy phase contents and grain size on the mechanical parameters were analyzed and a fracture mechanism was proposed.