Particle Deformation And Sliding During Compaction Of Spherical Powders : A Study By Quantitative Metallography
Published 1978 · Materials Science
The development of contact facets between particles during compaction of a spherical bronze powder is studied in isostatic and uniaxial compression. Nonradial particle motion (particle sliding or 'restacking') is revealed by the eccentricity of the contact flat with respect to the initial point of contact, the latter being marked by a neck formed during light presintering of the powder: bed. (The presintering does not seriously affect subsequent compaction.) From these observations, it is concluded that particle sliding occurs up to a pressure at which the original porosity has been about halved. The number of contacts per particle changes gradually from 7·3 in the uncompacted powder to about 12 at 2'5% residual porosity. At the end of densification, the contact number changes very quickly and the particle shape at full density can be approximated by a tetrakaidekahedron. The measurements of coordination number and contact flattening suggest that isostatic ompaction involves less sliding and more deformation of the particles than occurs in uniaxial compression.