MECHANISMS OF HOT-ISOSTATIC PRESSING.

A press was built which allows densification to be measured continuously during isostatic pressing of powders at temperatures up to 200 degree C and pressures up to 20 MN/m**2. The press was used to study the densification of lead, tin, and PMMA powders. The dominant mechanisms of densification were found to be plasticity and creep. Large discrepancies were detected between the data and previous models for these mechanisms. Improved models are presented which, while still approximate, include new physical ideas and give a better description of the experiments.