Tungsten-copper Powder Research Articles

Multiscale Numerical Simulation of the Shaped Charge Jet Generated from Tungsten-Copper Powder Liner

Formation process of the shaped charge jet of W-Cu powder liner was simulated with smoothed particle hydrodynamics (SPH) method of LS-DYNA software. With the digital image process technique and macro-micro coupling method, a multiscale finite element model was established, and the high speed deformation process of the microstructure driven by explosive detonation in the liner of shaped charge was successfully simulated. The Cu phases were susceptible to serious deformation while the tungsten phase has less deformation. Besides, the temperature field of the microstructure during the shaped charge deforming was calculated, and a discussion of the deformation mechanism of the liner was given. The methods proposed in this paper would be of help in microstructure design of shaped charge materials.

Sintering effect on the performance of tungsten-copper powder liner

In order to study the properties of high-temperature sintered tungsten-copper powder shaped charge liner, the tungsten powder and copper powder, whose particle size is below 20 μm, were chosen as the main material. The mixed powder were directly pressed into the desired shape of the charge liner by the top direct-pressure way. The microscopic morphology of the spinning shaped charge liner, and the particle properties of the copper and tungsten powder were studied with scanning electron microscopy. The experimental results showed that the irregular copper powder and regular tungsten powder both are effectively and hightemperature sintering, which can improve the compactness of the powder liner effectively. The wall thickness and density of the no sintered and sintered liner were tested, showing that sintering thinned down the wall thickness and improved the density. The penetration depth of no sintered powder liner, sintered powder liner and the spinning copper plate liner were respectively tested in different standoff, showing that the penetration properties of sintered powder liner are well.

Effects of phase size and addition of iron on sintering of tungsten-copper powder

Mixtures of single crystalline spherical W particles of 200–250 μm dia., fine W powder of 10 μm size and fine Ni powder were sintered at 167°C. Depending on the amount of liquid phase present complete densification is obtained after different sintering times and this is always accompanied by pronounced growth of the large W spheres at the expense of the smaller grains. With limited amounts of liquid phase present, under the influence of the densification force arising from the pores, grain growth occurs preferentially away from the areas where the grains are in close contact. Thus grain shape accommodation occurs during growth and this enables complete densification. In order to achieve rapid densification during liquid phase sintering, conditions of rapid grain growth are therefore favourable.Nous avons fritté à 1670°C des mélanges de particules sphériques monocristallines de W de 200 à 250 μm de diamètre, de fine poudre de W de 10 μm et de fine poudre de Ni. Nous obtenons une densification complète pour des durées de frittage qui dépendent de la quantité de phase liquide présente, et nous observons toujours une croissance importante des grandes sphères de W ou détriment des plus petits grains. Dans le cas d'une quantité limitée de phase liquide, la croissance des grains se produit préférentiellement en s'écartant des zones où les grains sont en contact étroit sous l'influence de la force de densification due aux pores. L'accommodation de la forme des grains se produit ainsi au cours de la croissance et elle permet une densification complète. Pour obtenir une densification rapide au cours du frittage en phase liquide, il faut se placer dans des conditions de croissance rapide des grains.Mischungen aus einkristallinen sphärischen W-Teilchen mit 200–250 μm Durchmesser, feinem W-Pulver von 10 μm Gröβe und feinem Ni-Pulver wurden bei 1670°C gesintert. Je nach dem Anteil an flüssiger Phase wird völlige Verdichtung nach verschiedenen Sinterzeiten erreicht. Die Verdichtung ist immer von ausgeprägtem Wachstum der groβen W-Kugeln auf Kosten der kleineren Körner begleitet. Für begrenzte Mengen an flüssiger Phase erfolgt unter der Wirkung der Triebkraft für Verdichtung das Wachstum der Körner bevorzugt abseits der Stellen, wo die Körner in nahem Kontakt stehen. Dadurch kommt es während des Kornwachstums zur Gestaltsangleichung der Körner, welche völlige Verdichtung ermöglicht. Um rasche Verdichtung während des Flüssigphasensinterns zu erzielen, sind deshalb Bedingungen für rasches Kornwachstum besonders günstig.

Structural inhomogeneity and localization of densification in the liquid-phase sintering of tungsten-copper powder mixtures

The size of the relative phase interface of a finely divided tungsten-copper mixture provides a measure of the uniformity of distribution of the phases in the mixture. A mixture with a large phase interface is not prone to localization of densification during LPS. In the particle size range of the refractory phase ensuring the necessary level of capillary forces, a high starting degree of homogeneity of a mixture with a small concentration of the low-melting-point component is an essential condition of its effective densification during LPS.

Effect of oxygen on the liquid-phase sintering of very fine tungsten-copper powder mixtures

A study was made of the processes of oxygen removal accompanying the sintering of blanks from W-30% Cu (TC) powder mixtures and of the effect of this refinement on their densification. It has been established that at 1100-1200/sup 0/C, oxygen-saturated copper does not wet tungsten. With a rise in temperature from 800-1000/sup 0/C, the solubility of hydrogen in copper increases threefold, and at the same temperature, the coefficient of diffusion of oxygen in copper is slightly smaller. A reduction in oxygen content to 0.03% in the sintering in hydrogen of parts of wall thickness greater than 10mm takes place only after the copper has melted.

Liquid-phase sintering of very fine tungsten-copper powder mixtures

The sintering of tungsten-copper powder mixtures of low copper content can be intensified by employing tungsten powders of submicron particle size. The process of liquid-phase sintering of very fine tungsten-copper powder mixtures can be quantitatively described within the framework of the theory of local heterogeneous deformation of a polycrystalline solid with allowance for diffusional grain shape accommodation.

CHARACTERIZATION OF THE DEGREE OF MIXING IN LIQUID-PHASE SINTERING EXPERIMENTS

Homogeneity of mixing plays an important role in liquid-phase sintering. In order to describe quantitatively the dependence of shrinkage on the degree of mixing, six different tungsten-copper powder mixtures were prepared. These powder blends were either presintered or sintered in the presence of liquid phase. The degree of mixing in both the presintered and liquid-phase sintered samples was determined by quantitative microstructural analysis. The developed method is well able to characterize the different state of mixing in the six powder blends on a microscopic scale. It is shown that a close relation exists between the microscopically characterized degree of mixing and densification during liquid-phase sintering.