Cu-Zn alloy

Brass alloys fall within the designation C205 to C280 and cover the entire soHd solution range of up to 35 wt % zinc in the Cu—Zn alloy system. 

Admiralty Brass and Naval Brass are 30 and 40% zinc alloys, respectively, to which a 1% tin addition has been added. Resistance to dezincification of Cu—Zn alloys is increased by tin additions. Therefore, these alloys are important for thein corrosion resistance in condenser tube appHcations. In these, as weU as the other higher zinc compositions, it is common to use other alloying additives to enhance corrosion resistance. In particular, a small amount (0.02—0.10 wt %) of arsenic (C443), antimony (C444), or phosphoms (C445) is added to control dezincification. When any of these elements are used, the alloy is referred as being "inhibited." For good stress corrosion resistance, it is recommended that these alloys be used in the fiiUy annealed condition or in the cold worked plus stress reHef annealed condition. 

Copper alloys include brasses (Cu-Zn alloys), bronzes (Cu-Sn alloys), cupronickels (Cu-Ni alloys) and nickel-silvers (Cu-Sn-Ni-Pb alloys). 

In this paper, the electronic structure of disordered Cu-Zn alloys are studied by calculations on models with Cu and Zn atoms distributed randomly on the sites of fee and bcc lattices. Concentrations of 10%, 25%, 50%, 75%, and 90% are used. The lattice spacings are the same for all the bcc models, 5.5 Bohr radii, and for all the fee models, 6.9 Bohr radii. With these lattice constants, the atomic volumes of the atoms are essentially the same in the two different crystal structures. Most of the bcc models contain 432 atoms and the fee models contain 500 atoms. These clusters are periodically reproduced to fill all space. Some of these calculations have been described previously. The test that is used to demonstrate that these clusters are large enough to be self-averaging is to repeat selected calculations with models that have the same concentration but a completely different arrangement of Cu and Zn atoms. We found differences that are quite small, and will be specified below in the discussions of specific properties. 

The free energy of mixing Umix for the fee Cu-Zn alloys is shown as a function of concentration in Fig. 1. It is obtained from the usual formula... 

PCu(ci,q) is clearly not a 5-function as has been suggested. Many more LSMS calculations would have to be done in order to determine the structure of Pcn(ci,q) for fee alloys in detail, but it is easier to see the structure in the conditional probability for bcc alloys. The probability Pcu(q) for finding a charge between q and q-t-dq on a Cu site in a bcc Cu-Zn alloy and three conditional probabilities Pcu(ci,q) are shown in Fig. 6. These functions were obtained, as for the fee case, by averaging the LSMS data for the bcc alloys with five concentrations. The probability function is not a uniform function of q, but the structure is not as clear-cut as for the fee case. The conditional probabilities Pcu(ci,q) are non-zero over a wider range than they are for the fee alloys, and it can be seen clearly that they have fine structure as well. Presumably, each Pcu(ci,q) can be expressed as a sum of probabilities with two conditions Pcu(ci,C2,q), but there is no reason to expect even those probabilities to be 5-functions. 

Pickering, H. W. and Byrne, P. J., Partial Currents During Anodic Dissolution of Cu-Zn Alloys at Constant Potential , J. Electrochem. Soc., 116, 1492 (1968)... 

Intergranular corrosion Carbon steels in NO solns Some Al alloys in Cl Cu-Zn alloys solns, high in NH7 solns potentials Fe-Cr-Ni steels in Cl solns Cu-Zn alloys Mg-A alloys in NO in CrO + solns Cl solns Ti alloys in High methanol. A strength alloys, low steels in Cl potentials solns Brittle fracture... 

Ni-Mo alloy, similar to Hastelloy B see Bahler Superantinit Cast Si-Fe with 18% Si Cu-Zn alloy with 72-90% Cu... 

There are two important hydrogenation (or reduction) — titration procedures for the detn of N as ammonia. The Devarda method involves the quant reduction of nitrates to ammonia in alkaline soln using an Ai-Cu-Zn alloy. The ammonia evolved is distd into standard sulfuric acid... 

Hume-Rothery phases (brass phases, electron compounds ) are certain alloys with the structures of the different types of brass (brass = Cu-Zn alloys). They are classical examples of the structure-determining influence of the valence electron concentration (VEC) in metals. VEC = (number of valence electrons)/(number of atoms). A survey is given in Table 15.1. 

Brass (Cu-Zn alloy) is highly workable and has an impressive gold shine. 

Several binary alloys of technological importance are known to form by way of an underpotential co-deposition mechanism. The abnormal composition-potential relationship observed in Cu-Zn alloys deposited from cyanide-based electrolytes, one of the most widely used commercial alloy plating processes, is attributed to the underpotential co-deposition of Zn [64]. The UPD of Zn is also known to occur on Co and Fe and has been included in treatments focusing on the anomalous co-deposition of Co-Zn [65] and Ni-Zn alloys [66-68]. Alloys of Cu-Cd have been shown to incorporate Cd at underpotentials when deposited from ethylene diamine solution [69-71]. 

As discussed below in the section on Cu catalysts, it has been noted that Cu/ZnO catalysts have low activities and deactivate quickly in the decomposition reaction. However, the inclusion of nickel, introduced in co-precipitation preparation, has been reported to enhance initial activity and retard deactivation.29 The role of nickel has been ascribed to an increase in dispersion of the active Cu species and also the prevention of deactivation via the formation of Cu-Zn alloys. 

Budd, P.D., Lythgoe, P., McGill, R.A.R., Pollard, A.M. and Scaife, B. (1999). Zinc fractionation in liquid brass (Cu/Zn) alloy potential environmental and archaeological applications. In Geoarchaeology Exploration, Environments, Resources, ed. Pollard, A.M., Special Publication 165, Geological Society, London, pp. 147-153. 

Spinning Cup Atomization (RSC) <10-300 Standard deviation 1.5-1.7 Sn, Pb, Al, Cu, Zn alloys, Stainless and High speed tool steels, Superalloys 105-106 — 0.5-1.4x 10 3 Fine, clean, spherical particles, Narrow size distribution Small facility Relatively low volume productivity... 

Electrodeposited binary alloys may or may not be the same in phase structure as those formed metallurgically. By way of illustration, we note that in the case of brass (Cu-Zn alloy), x-ray examination reveals that apart from the superstructure of... 

In ZnCl2-EMIC (1 1) melt containing Cu(I), the electrodeposition of Cu-Zn alloys on tungsten and nickel electrodes was carried out [180]. The composition of the Cu-Zn deposit was changed by deposition potential, temperature, and Cu(I) concentration in a plating bath. 

The most famous example of the crystal structure correlating with the average number of valence electrons per atom or band filling, N, is the Hume-Rothery alloy system of noble metals with sp-valent elements, such as Zn, Al, Si, Ge, and Sn. Assuming that Cu and Ag have a valence of 1, then the fee -phase is found to extend to a value of N around 1.38, the bcc / -phase to be stabilized around 1.48, the -phase around 1.62, and the hep e-phase around 1.75, as illustrated for the specific case of Cu-Zn alloys in Fig. 6.15. In 1936 Mott and Jones pointed out that the fee and bcc electron per atom ratios correlate with the number of electrons required for a free-electron Fermi sphere first to make contact with the fee and bcc Brillouin zone faces. The corresponding values of the Fermi vector, fcF, are given by... 

Figure 6.16 shows recent results of a Jones-type analysis of the stability of Cu-Zn alloys within the rigid-band approximation. This latter approximation assumes that the bands of fee, bcc, and hep copper remain unchanged (or rigid) on alloying, so that the structural energy difference between any two lattices is given by... 

Fig. 16. Dehydrogenation of formic acid on the Cu/Zn alloys [G. M. Schwab and S. Pesmatjoglou, J. Phys. Chem. 62, 1046 (1948)].

Electrodeposited binary alloys may or may not be the same in phase structure as those formed metallurgically. By way of illustration, we note that in the case of brass (Cu-Zn alloy), X-ray examination reveals that, apart from the superstructure of /3-brass, virtually, the same phases occur in the alloys deposited electrolytically as formed in the melt. Phase limits closely agree with those in the bulk. Debye-Scherrer interference rings indicate the presence of a strong distortion of the lattice, particularly in the a-phase brass. Electrodeposited a-brass, for instance, is... 

In relation to the discussed syntheses, we emphasize the systematic study of the kinetics of metal dissolution [202,657-659]. Also, the oxidation of Cu—Zn alloy was studied [658], which opens a route to simple preparation of heteronuclear complexes. 

At 1273K, a copper-zinc alloy containing 16mol% Zn lies on the solidus, and that on the liquidus contains 20.6mol% Zn. The activity coefficient of Zn in liquid Cu-Zn alloys, relative to the pure liquid zinc standard state, is represented by... 

Zinc oxide is a very old technological material. Already in the Bronze Age it was produced as a byproduct of copper ore smelting and used for healing of wounds. Early in history it was also used for the production of brass (Cu-Zn alloy). This was the major application of ZnO for many centuries before metallic zinc replaced the oxide [149]. With the start of the industrial age in the middle of the nineteenth century, ZnO was used in white paints (chinese white), in rubber for the activation of the vulcanization process and in porcelain enamels. In the following a number of existing and emerging electronic applications of ZnO are briefly described. 

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