AN ANALYSIS OF THE CAN EFFECT IN AN ISOSTATIC PRESSING OF COPPER-POWDER

Based on an elastic-plastic analysis of the can deformation, experimental data from Wadley et al. (1991, Acta Metall. Mater. 39, 979) are used to evaluate the shielding effect of the can in an isostatic pressing of copper powder. The calculation indicates that the consolidation of the powder compact is preceded by a stage of powder rearrangement. Thereafter, during consolidation, it is found that in this particular case, compressive stresses in the powder are about 20 MPa less than the pressure applied to the exterior of the can. Furthermore, the powder is not in a state of hydrostatic pressure. The axial compressive stress in the powder is less than the transverse compressive stress. This effect is due to the can which supports a larger load in the axial direction compared to the radial direction during plastic deformation. A model for the nonisostatic yielding of metal powder is compared to the data. It is found that strain hardening must be allowed for to get agreement between the model and the experiment for cold pressing.