Densification dynamics of copper and iron powder billets in hot shock compaction: Simulation and analysis

The paper presents the results from computer simulation and analysis of experimental data on the densification of copper and iron powder billets during hot shock compaction. It is established for the first time that the shear viscosity of the porous material matrix shows a stronger dependence on the initial impact velocity than the billet temperature does. The estimated activation energy of the viscous flow in the matrix is equal to 0.35 eV for copper, 0.3 eV for α-Fe, and 0.5 eV for γ-Fe.     

Structure and Certain Properties of Hot-Pressed Boron Carbide-Based Ceramic with Calcium-Silicon Additive

The influence which the composition of powder mixtures, the treatment conditions which the mixtures are subjected to, and the conditions under which the hot-pressed composite materials B₄C – (5-10 mass%) calcium-silicon are fabricated exert on the structure, nature of failure, and mechanical properties of these materials is investigated. Optimum properties are possessed by material containing 10 mass% of addition. It is shown that the structure, morphology, and dispersivity, as well as the nature of the distribution of the components that are added to the composite material (secondary phase) vary as the temperature of hot pressing changes. Maximal mechanical characteristics of the composite material (σ_bend = 560 MPa, K _1c = 4.7 MPa·m^1/2, HV = 37 GPa) are attained at hot-pressing temperatures in the range 2000-2100°C.     

Influence of addition of calcium hexaboride on the structure and properties of hot-pressed titanium boride ceramic

In our study of the microstructure of hot-pressed TiB₂—x CaB₆ specimens we have found that the amount of CaB₆ added affects the grain size. The TiB₂ grain size decreases when the CaB₆ content in the composite exceeds 5%. The retardation of the grain growth during hot pressing of powder with the composition TiB₂—10% CaB₆ is attributed to dissolution of Ca in it. A composite with that composition has a high microhardness and bending strength.     

Calculation and experimental determination of pressure in impact hot pressing

Conclusions Within the framework of the rheological theory an analysis was made of the densification of porous iron compacts during impact hot pressing, and the results obtained were employed for constructing curves of pressure variation as a function of relative density. During a short time of densification of material, of the order of 1 msec, high pressures, of several tons per square centimeter, were found to be generated under the action of an impact energy of 3000–7000 J at a striker mass of 50 kg. Good agreement was obtained between calculated and experimental oscillograms of pressure and also their maximum values. At densities approaching the theoretical, calculated pressures proved to be higher than experimental values because in the calculations no allowance was made for the compressibility of the solid phase of the porous solid.Translated from Poroshkovaya Metallurgiya, No. 6(210), pp. 40–45, June, 1980.