Evolution of mechanical properties of porous alumina during free sinteringand hot pressing

This comparative study addresses the influence of microstructural evolution on mechanical properties of porous alumina sintered with and without the a pplication of uni-axial pressure. A complete set of data on Young's modulus , long-crack fracture toughness, and fracture strength for two alumina powd ers as a function of density was obtained. The evolution of fracture streng th with increased density was modeled using a porosity-dependent crack-tip fracture toughness, linked to the contact area of grains and a porosity-dep endent size of the largest defect. The defect shape factor was found indepe ndent of porosity. A uniaxial pressure of 13 MPa during densification had n egligible effect on the relation of strength to porosity.