THE SURFACE-TOPOGRAPHY OF COMPACTED AGGLOMERATES - A MEANS TO OPTIMIZE COMPACTION CONDITIONS

The measurement and quantification of the surface topography of single -ended die-pressed cylindrical compacts, prepared using agglomerated a lumina powders at various values of compaction pressure and cylinder a spect ratio, are described and a means to study the deformation and br eakdown of the agglomerates at the die walls is evaluated. A specially constructed non-contacting laser scanning profilometer, with associat ed hardware and software, is described and has been used to obtain the surface topographical profiles of the green alumina compacts. Selecte d data are reported and interpreted using conventional roughness param eters, autocorrelation functions, and bearing area curves. These compu ted parameters are used to elucidate the deformation characteristics o f the agglomerates within the compacts. The deformation of the alumina agglomerates, at the planar (upper and lower) surfaces of the compact s, commences at very low compaction pressures and the inter-agglomerat e surface pores are eventually annihilated at relatively high compacti on pressures. The optimum normal pressure for the elimination of these inter-agglomerate surface pores, in the present alumina system, was d etermined as 74 MPa. The results obtained from the curved surface prof iles of the compacts, as a function of the distance from the compressi on source, show that the wall normal pressure distribution, along the height of the compact, decreases exponentially as a function of the he ight of the compact (from top to bottom).