Phase diagrams copper-zinc

Phase diagrams have been measured for almost any alloy system you are likely to meet copper-nickel, copper-zinc, gold-platinum, or even water-antifreeze. Some... 

Fig. 3.6. (a) The copper-nickel diagram is a good deal simpler than the lead-tin one, largely because copper and nickel are completely soluble in one another in the solid state. (b) The copper-zinc diagram is much more involved than the lead-tin one, largely because there are extra (intermediate) phases in between the end (terminal] phases. However, it is still an assembly of single-phase and two-phase fields. 

Figure A1.19 shows the phase diagram for the copper-zinc system. It is more complicated than you have seen so far, but all the same rules apply. The Greek letters (conventionally) identify the single-phase fields. 

The copper-zinc system (which includes brasses) has one eutectoid reaction. Mark the eutectoid point on the phase diagram (Fig. A 1.38). 

Sodium-zinc alloys for phase diagram determination are prepared by melting the elements in glass tubes under H2- Samples of NaZujj are prepared by heating zinc for several hours above the melting point of NaZn,3 (557°C) with xs Na in alundum extraction thimbles with N2 or Ar in a steel bomb scaled with copper gaskets. Excess Na was removed by extraction with liq NHj. Both KZn,3 and KCd,2 were prepared in this manner. ... 

Abstract In the beginning, the mixed potential model, which is generally used to explain the adsorption of collectors on the sulphide minerals, is illustrated. And the collector flotation of several kinds of minerals such as copper sulphide minerals, lead sulphide minerals, zinc sulphide minerals and iron sulphide minerals is discussed in the aspect of pulp potential and the nature of hydrophobic entity is concluded from the dependence of flotation on pulp potential. In the following section, the electrochemical phase diagrams for butyl xanthate/water system and chalcocite/oxygen/xanthate system are all demonstrated from which some useful information about the hydrophobic species are obtained. And some instrumental methods including UV analysis, FTIR analysis and XPS analysis can also be used to investigated sulphide mineral-thio-collector sytem. And some examples about that are listed in the last part of this chapter. 

It is necessary to establish a foundation of definitions and basic concepts relating to alloys, phases, and equilibrium before delving into the interpretation and utilization of phase diagrams. The term component is frequently used in this discussion components are pure metals and/or compounds of which an alloy is composed. For example, in a copper-zinc brass, the components are Cu and Zn. Solute and solvent,... 

In addition to the eutectic, other invariant points involving three different phases are found for some aUoy systems. One of these occurs for the copper-zinc system (Figure 9.19) at 560°C (1040°F) and 74 wt% Zn-26 wt% Cu. A portion of the phase diagram in this vicinity is enlarged in Figure 9.21. Upon coohng, a solid 8 phase transforms into two other solid phases (y and e) according to the reaction... 

Figure 9.21 A region of the copper-zinc phase diagram that has been enlarged to show eutectoid and peritectic invariant points, labeled E (560°C, 74 wt% Zn) and P (598°C, 78.6 wt% Zn), respectively.

The most common copper alloys are the brasses, for whieh zine, as a snbstitntional impurity, is the predominant alloying element. As may be observed for the eopper-zinc phase diagram (Figure 9.19), the a phase is stable for eoneentrations up to approximately 35 wt% Zn. This phase has an FCC crystal structure, and a-brasses are relatively soft, ductile, and easily cold worked. Brass alloys having a higher zinc content contain both a and p phases at room temperature. The P phase has an ordered BCC crystal structure and is harder and stronger than the a phase consequently, a + p alloys are generally hot worked. 

In a diagram of a cell a single vertical line conventionally represents a phase boundary at which a potential difference is taken into account. A double vertical line represents a liquid junction at which the potential difference is ignored or is considered to be eliminated by an appropriate salt bridge. For example, a cell consisting of zinc and copper half-cells can be expressed by... 

When we compare, for example, the ordinary per cent, by weight equilibrium diagrams of the alloys of monovalent copper with, first, divalent zinc, second, trivalent aluminium, and, third, tetravalent tin, we find that each system is characterised by similar a, a + / , /3, /3 + y, y, etc., phase areas. We have already noted that the range of a-solid solution decreases with increasing valency of solute, and that the maximum solid solubility, in each case, occurs at an electron concentration of 1 4 (p. 69). 

This is the zinc-copper cell depicted in Fig. 14.2 on the next page, sometimes called a Daniell cell. The two electrolyte phases are separated by a liquid junction represented in the cell diagram by the dashed vertical bar. If the liquid junction potential can be assumed to be negligible, the liquid junction is instead represented by a pair of dashed vertical bars ... 

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