THE COMPACTION OF METAL POWDERS BY ROLLING. I.—THE PROPERTIES OF STRIP ROLLED FROM COPPER POWDERS

Abstract

The investigation described is an extension of earlier work (“Symposium on Powder Metallurgy 1954”, p. 131. 1956: London (Iron and Steel Institute), and Sheet Metal Ind., 1955, 32, 589) which described the effect of rolling pressure and sintering conditions on the mechanical properties of strip rolled from copper powders. The directional variation of U.T.S. and of elongation of sintered strip are shown to be the same as those of solid copper with a similar microstructure, at least for material with up to 16% porosity. The shape of powder particles and the particle-size distribution have a marked effect on the strength of sintered strip by virtue of their effect on the shape and size of the pores in the sintered material. Measurements of electrical resistance reveal a linear relationship between conductivity and porosity over wide ranges of porosity in both “green” and sintered strip. The conductivity increases rapidly during the first few minutes of sintering at 1000° C. Measurements of the resistance in the rolling direction and in the transverse direction, which are independent of local variations in density, have been made on green sheet; the resistance in the rolling direction is the higher. A correlation between this result and the mode of particle deformation is proposed, and is elaborated in Part II of this paper.