Phase diagrams copper-silver

Fig. 2. Liquidus of isotherms of gold-copper-silver alloys and phase diagrams of the binary constituents (83).

Fig. 20.41 (a) Silver-copper phase. diagram and (b) magnesium-tin phase diagram... 

No phase diagram is available for the potassium-copper or potassium-silver systems. A diagram for the potassium-gold system shows the existence of four intermediate phases but later work shows that the phase identified as KAU4 1 diagram is in fact KAuj. 

Phase diagrams for the systems silver/copper (limited solubility in the solid) and aluminum/silicon (formation of an eutectic mixture)... 

P. R. Subramanian and J. H. Perepezko, Ag-Cu (silver-copper) system, in Phase Diagrams of Binary Copper Alloys (P. R. Subramanian, D. J. Chakrabarti and D. E. Laughlin, eds.). Materials Park, OH ASM International, 1994. 

Other two-component systems may exhibit either limited solubility or complete insolubility in the solid state. An example with limited solubUity is the silver-copper system, of which the reduced-phase diagram is shown in Figure 13.5. Region L represents a liquid phase, with F = 2, and S and 5s represent solid-solution phases rich in Ag and Cu, respectively, so they are properly called one-phase areas. S2 is a two-phase region, with F= 1, and the curves AB and DF represent the compositions of the two solid-solution phases that are in equilibrium at any... 

Partial Miscibility in the Solid State So far, we have described (solid + liquid) phase equilibrium systems in which the solid phase that crystallizes is a pure compound, either as one of the original components or as a molecular addition compound. Sometimes solid solutions crystallize from solution instead of pure substances, and, depending on the system, the solubility can vary from small to complete miscibility over the entire range of concentration. Figure 14.26 shows the phase diagram for the (silver + copper) system.22 It is one in which limited solubility occurs in the solid state. Line AE is the (solid -I- liquid) equilibrium line for Ag, but the solid that crystallizes from solution is not pure Ag. Instead it is a solid solution with composition given by line AC. If a liquid with composition and temperature given by point a is... 

Consider a binary alloy of copper and silver. At a temperature near 850 °C and an alloy composition near 80% Cu-20% Ag, the phase diagram says that there should be a copper-rich solid and a liquid. Considering the pressure to be fixed at one atmosphere but allowing temperature variations,... 

The silver-copper phase diagram. Reprinted with permission of ASM International from L. A. Willey, Metals Handbook, vol. 8, 8th ed. (Materials Park, OH ASM, 1973), p. 259. All rights reserved, www.asminternational.org. 

Both silver and gold form ideal solid solutions with palladium. However, stoichiometric compositions with unique properties, such as in Hunter s preferred membrane composition of PdsAg, [31], might suggest the possibility of intermetallic compounds or ordered structures differing from that of the ideal solutions [35]. Palladium and copper also form ideal solid solutions, but in this system phase diagrams clearly show additional phases with crystal structures differing from the parent fee phase of the solid solutions. 

With respect to the phase diagram of the copper-silver system (Figure 8.28) ... 

The absence of any phase diagram data for multicomponent systems necessitated some preliminary experiments to establish the interaction between a series of A and pompounds. We did not restrict ourselves to solid solutions with compounds containing copper put also included compounds in which the element of group I was silver. A detailed study of ternary silver compounds showed that it was impossible to obtain them by direct synthesis irom the elements. 

Figure 13.2 shows two temperamre-composition phase diagrams with single eutectic points. The left-hand diagram is for the binary system of chloroform and carbon tetrachloride, two liquids that form nearly ideal mixmres. The solid phases are pure crystals, as in Fig. 13.1. The right-hand diagram is for the silver-copper system and involves solid phases that are solid solutions (substimtional alloys of variable composition). The area labeled s is a solid solution that is mostly silver, and s is a solid solution that is mostly copper. Tie lines in the two-phase areas do not end at a vertical line for a pure solid component as they do in the system shown in the left-hand diagram. The three phases that can coexist at the eutectic temperature of 1,052 K are the melt of the eutectic composition and the two solid solutions.

Figure 6.18 shows the solid-liquid temperature-composition phase diagram of silver and copper at 1.00 atm. There are two one-phase regions of limited solid solubility, labeled a and /3. A tie line in the area between the a and P regions represents two coexisting saturated solid solutions, one that is mostly silver and one that is mostly copper. The tie line at 779°C connects the points representing the two solid phases and one liquid phase that can be at equilibrium with the two solid phases. The point representing this liquid phase is called the eutectic point. If a liquid that has the same composition as the eutectic is cooled, two solid phases will freeze out when it reaches the eutectic temperature, with compositions represented by the ends of the tie line. 

Figure 6.18 Solid-Liquid Tennperahire-Composition Phase Diagram of Silver and Copper. From R. E. Dickerson, MolecularThermodynamics, W. A. Benjamin, Inc., New York, 1969, p. 371.

As silver is added to copper, the temperature at which the alloys become totally liquid decreases along the liqnidns line, line AE thus, the melting temperature of copper is lowered by silver additions. The same may be said for silver the introduction of copper reduces the temperature of complete melting along the other liquidus line, FE. These liquidus lines meet at the point E on the phase diagram, which point is designated by composition and temperature Te, for the copper-silver system, the values for these two parameters are 71.9 wt% Ag and 779°C (1434°F), respectively. It should also be noted there is a horizontal isotherm at 779°C and represented by the line labeled BEG that also passes through point E. 

Another common eutectic system is that for lead and tin the phase diagram (Figure 9.8) has a general shape similar to that for copper-silver. For the lead-tin system, the solid-solution phases are also designated by a and /3 in this case, a represents a solid solution of tin in lead for (3, tin is the solvent and lead is the solute. The eutectic invariant point is located at 61.9 wt% Sn and 183 C (361 F). Of course, maximum solid solubility compositions as well as component melting temperatures are different for the copper-silver and lead-tin systems, as may be observed by comparing their phase diagrams. 

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