Copper-zinc alloys phase diagrams

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... 

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. ... 

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,... 

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. 

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). 

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