Geometrical change in metallic hollow spheres (MHSs) during compression at elevated temperatures is formulated by using the results of the viscoplastic finite element analysis of a unit cell model. The parameters related to the viscosity, contact area and diametral area of MHSs are approximated by functions of the shell thickness, and placed into a constitutive equation for the sintering of powder particles. Pressure sintering of iron hollow sphere compacts is also performed in a tube with weights. The reduction in height of the compacts varies with the shell thickness of the MHS and the pressure and temperature during sintering. The compressive behavior of the compacts in the firing process is predicted well by the proposed constitutive equations.
