Alloy dispersion-hardened

Ultrasonic Atomization 30-50 USWA >100 Medium size distribution Solder materials, Welding electrodes, Ag-, Cu-base alloys, Dispersion-hardened allovs USWA 107 0.02-0.8 Low Spherical high quality particles, Low cost, Small unit, High EE Low volume productivity... 

Key words high-strength aluminum alloys, dispersion hardening, quasicrystals, eutectic alloys, mechanical properties... 

Sohd rocket propellants represent a very special case of a particulate composite ia which inorganic propellant particles, about 75% by volume, are bound ia an organic matrix such as polyurethane. An essential requirement is that the composite be uniform to promote a steady burning reaction (1). Further examples of particulate composites are those with metal matrices and iaclude cermets, which consist of ceramic particles ia a metal matrix, and dispersion hardened alloys, ia which the particles may be metal oxides or intermetallic compounds with smaller diameters and lower volume fractions than those ia cermets (1). The general nature of particulate reinforcement is such that the resulting composite material is macroscopicaHy isotropic. 

Copper. The physical properties of pure copper are given in Table 11. The mechanical properties of pure copper are essentially the same as those for ClOl and CllO. The coppers represent a series of alloys ranging from the commercially pure copper, ClOl, to the dispersion hardened alloy C157. The difference within this series is the specification of small additions of phosphoms, arsenic, cadmium, tellurium, sulfur, zirconium, as well as oxygen. To be classified as one of the coppers, the alloy must contain at least 99.3% copper. 

Additions of antimony, bismuth and tin to the lead appear to be detrimental. There is an indication that the addition of 0 - l<7o Ag is almost as effective as 1% and additions as low as 0-01% has been utilised in practice. Dispersion-hardened lead alloys have been unsatisfactory, showing pronounced spalling in the direction of extrusion. Pb-0-lTe-0-lAg has been also used with apparent success" . 

Dispersion devices, ozone, 17 801-802 Dispersion force, 12 4 Dispersion-free solvent extraction, 10 766 Dispersion hardening, 13 501, 502, 527 of refractory metal alloys, 13 528 Dispersion polymerization, 24 156-157 of acrylamide polymers, 1 323 of methacrylic ester polymers, 16 289 Dispersion processing of FEP polymer, 18 314... 

One important class of particulate composites is dispersion-hardened alloys. These composites consist of a hard particle constituent in a softer metal matrix. The particle constituent seldom exceeds 3% by volume, and the particles are very small, below micrometer sizes. The characteristics of the particles largely control the property of the alloy, and a spacing of 0.2-0.3 tim between particles usually helps optimize properties. As particle size increases, less material is required to achieve the desired interparticle spacing. Refractory oxide particles are often used, although intermetallics such as AlFes also find use. Dispersion-hardened composites are formed in several ways, including surface oxidation of ultrafine metal powders, resulting in trapped metal oxide particles within the metal matrix. Metals of commercial interest for dispersion-hardened alloys include aluminum, nickel, and tungsten. 

A cermet is a particulate composite similar to a dispersion-hardened alloy, but consists of larger ceramic grains (cer-) held in a metal matrix (-met) (see Figure 1.78). The refractory particulates can be from the oxide category, such as alumina (AI2O3),... 

Figure 1.78 Comparison of (a) cermet and (b) dispersion-hardened alloy. Reprinted, by permission, from M. Schwartz, Composite Materials Handbook, 2nd ed., p. 1.32. Copyright 1992 by McGraw-Hill.

Dan] Dannoehl, W., About Magnetic Behaviour of the Ferrite Dispersion Hardening in Iron-Nickel-Copper Alloys (in German), Z. Metallkd., 30(3), 95-99 (1938) (Experimental, Magn. Prop., Phase Relations, 22)... 

Even this definition needs to be classified [7, 8]. To some researchers it is still too broad because it includes many materials that are not usually thought of as composites such as concrete, copolymers and blends, reinforced plastics, and carbon-black-filled rubber. On the other hand, some of the more recent composites are excluded from the category of composites if this definition is strictly applied. For example, many particulate-type composites such as dispersion-hardened alloys and cermets have composite structures that are microscopic rather than macroscopic [2,8]. In some cases, the composite structures are nano-scopic, with the physical constraint of several nanometers as the minimum size of the components [9-16]. The terms... 

Silver, Au, Pd, and Pt are comparatively soft and ductile. Their hardness increases in the order Rh < Ir < Ru < Os. Strengthening of the alloys is affected by solid solution and dispersion hardening. The corrosion resistance against different agents decreases in the order Ir > Ru > Rh > Os > Au > Pt > Pd > Ag. 

Data for self-diffusion of Ag in Ag alloys and diffusion of tracer impurity elements are shown in Tables 3.1-153-3.1-158 and Figs. 3.1-210-3.1-212. Diffusion of H and O is of importance for annealing treatments and dispersion hardening [1.217,220,226,235]. 

Clauer, A. H. Wilcox, B. A. (1972). The Role of Grain Size and Shape in Strengthening of Dispersion Hardened Nickel Alloys. Acta Metallurgica, Vol. 20, No. 5, pp. 743-757, ISSN 00016160... 

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