Effect of cold isostatic pressing on microstructure and shrinkage anisotropy during sintering of uniaxially pressed alumina compacts

The effect of cold isostatic pressing (CIP) on microstructure and shrinkage anisotropy during sintering is systematically and quantitatively examined for uniaxially pressed alumina compacts made from spray-dried granules. This study helps to clarify the abnormal effect of CIP on their sintering behavior. Uniaxial pressing caused anisotropic deformation of granules in the compacts, making spherical granules into an elliptical shape and developing the arrangement structure of particles. A subsequent CIP slightly reduced the apparent deformation of granules, but increased the degree of particle arrangement evaluated by optical microscopy. It also increased the shrinkage anisotropy of the compacts during sintering. The experimental results indicated that there was a linear relationship between the degree of particle arrangement and the shrinkage anisotropy during sintering when employing the pressed alumina compacts.