Effect of Molecular Interaction on Strength of Green Compacts

Abstract

Modern approaches to calculating the strength of green compacts by van-der-Waals force (σ_ВВ) are reviewed. For tested powders of metals (Al, Zn, Cu, Ni and Mo) and one nonmetal (FeSi), the respective components (σ_ВВ) are calculated and green tensile strength (σ_вн.ср) is experimentally determined. Comparison of σ_вн.ср /σ_ВВ correlations shows that σ_вн.ср and σ_ВВ are of one order for the atomized zinc powder, and σ_ВВ is greater than σ_вн.ср, for the atomized copper powder, though σ_вн.ср is greater than σ_ВВ by 2 to 3 orders for most powders with irregular shape of particles. This difference can be attributed to the effect of particle shape and mechanical locking or wedging of particles when compacted. To predict the green strength, it is necessary to take into account both the shape of particles (or relative apparent density of powder) and the temperature conditions of formation.