Equilibrium diagram

Frankenthal R P and Kruger J (eds) 1984 Equilibrium Diagrams of Localized Corrosion Proc. vol 84-9 (Pennington, NJ Electrochemical Society)... 

System in which the solid phases consist of the pure components and the components are completely miscible in the liquid phase. We may now conveniently consider the general case of a system in which the two components A and B are completely miscible in the liquid state and the solid phases consist of the pure components. The equilibrium diagram is shown in Fig. 1,12, 1. Here the points A and B are the melting points of the pure components A and B respectively. If the freezing points of a series of liquid mixtures, varying in composition from pure A to pure B, are determined, the two curves represented by AC and BC will be obtained. The curve AC expresses the compositions of solutions which are in equilibrium, at different temperatures, with the solid component A, and, likewise, the curve BC denotes the compositions... 

By constructing cooling curves for several mixtures of different composition, the total weight of the mixture being kept the same in each case, a series of cooling curves may be obtained which may be employed for the construction of the equilibrium diagram. Thus in Fig. /, 13, 2, a. 

Another procedure, known as the thaw melt method, is available for the construction of equilibrium diagrams it involves heating, instead of... 

The general case of two compounds forming a continuous series of solid solutions may now be considered. The components are completely miscible in the sohd state and also in the hquid state. Three different types of curves are known. The most important is that in which the freezing points (or melting points) of all mixtures lie between the freezing points (or melting points) of the pure components. The equilibrium diagram is shown in Fig. 7, 76, 1. The hquidus curve portrays the composition of the hquid phase in equihbrium with sohd, the composition of... 

Fig. 11. (a) Equilibrium isotherm and (b) dimensionless equilibrium diagram showiag favorable, linear, and unfavorable isotherms. 

The phases present in products can differ from those predicted from equilibrium diagrams. Nonequilibrium metastable phases form at solidification rates experienced in commercial ingots. Because of the low rate of diffusion of iron in alurninum, equilibrium conditions can only be established by long heat treatments and are very slowly approached at temperatures below about 550 °C. Small additions of other elements, particularly manganese, can also modify the phase relations. 

The iron-carbon solid alloy which results from the solidification of non blastfurnace metal is saturated with carbon at the metal-slag temperature of about 2000 K, which is subsequendy refined by the oxidation of carbon to produce steel containing less than 1 wt% carbon, die level depending on the application. The first solid phases to separate from liquid steel at the eutectic temperature, 1408 K, are the (f.c.c) y-phase Austenite together with cementite, Fe3C, which has an orthorhombic sttiicture, and not die dieniiodynamically stable carbon phase which is to be expected from die equilibrium diagram. Cementite is thermodynamically unstable with respect to decomposition to h on and carbon from room temperature up to 1130 K... 

The equilibrium diagram or phase diagram summarises the equilibrium constitution of the alloy system. 

W. Hume-Rothery, ]. W. Christian and W. B. Pearson, Metallurgical Equilibrium Diagrams, Institute of Physics, 1952. 

DEF. An equilibrium-constitution diagram or equilibrium diagram for short (or, shorter still, phase diagram), is a diagram with T and Xg (or Wg) as axes. It shows the results of experiments which measure the equilibrium constitution at each T and Xg (or Wg). 

A hypothetical equilibrium diagram between two elements A and B shows the following features ... 

Draw the equilibrium diagram assuming all phase boundaries are straight lines. 

For any particular system, a graph can be constructed using the concentration of the solute in the liquid phase (Ca) and the concentration or partial pressure of the solute in the gas phase (Pa) as the abscissa and ordinate, respectively. A line indicating the equilibrium concentrations of the solute in the gas and solvent drawn on this graph, results in an equilibrium diagram. 

A typical equilibrium diagram is shown on Figure 8. As noted earlier, a counter-current flow scrubber provides the highest efficiency of operation. The respective concentrations and rates, as shown in Figure 9 provide the basis for a material balance across this scrubber design. 

Lj and are the pure liquid and inert gas loading rates, respectively, in units of Ib-moles/hr-ft. The second expression is the operating line on an equilibrium diagram. In all scrubbing application, where the transfer of solute is from the gas to the liquid, the operating line will lie above the equilibrium curve. When the mass transfer is from the liquid to the gas phase, the operating line will lie below the equilibrium curve. The latter case is known as stripping . 

Figure 45. Futjural-ethylene glycol-water phase equilibrium diagram.

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