Liquids liquidus surface

Equations (A5) and (A6) describe the interspecies equilibrium in the liquid phase for some composition xlt x2. If this liquid is on the liquidus surface of Ax BuC(s), then the liquidus equations given by Eqs. (12) and (13) must also be satisfied. Using the general relation between relative chemical potential and activity coefficient given by Eq. (60), the liquidus equations are... 

Fig. 38. Liquidus surface in the Hg-Cd-Te system on the Hg-Cd-rich side of the HgTe-CdTe pseudobinary section. The liquidus temperature in degrees Celsius is plotted against the atom fraction of for fixed values of z that are shown along the right vertical axis. The composition of the liquid phase is written as (Hg , Cdz),Te, y. Experimental points shown as symbols. The single diamond point is for = 0.09. Arrows below each liquidus lines indicate where the atom fractions of Cd and are equal.

Fig. 41. The partial pressure of mercury in atmospheres plotted against 103 times the reciprocal absolute temperature for a traverse across the liquidus surface such that the atom fractions Cd and are always equal. The number near each circle give the atom fraction of mercury in the liquid phase at the pressure and temperature specified by the circle. 

Finally, Table XIII gives a tabulation of liquid composition, liquidus temperature, x value of the coexisting solid, and mercury pressure at the liquidus temperature. The table is arranged in sections for different z values in the liquidus composition (Hg, CdJyTe, r Since the calculated liquidus surface for -rich compositions and high temperatures is given only for z values up to 0.5 in Fig. 27, entries with less than j are also included for the high z values. 

These lines are called liquidus isotherms. The intersections of adjoining liquidus surfaces like ae, be and ce are called the boundary curves. When a liquid whose composition lies in the region surrounded by Aceh is cooled, the first crystalline phase that appears is A, and hence A is called the primary phase and the region Aceh is the primary field of A. In this field, solid A is the last solid to disappear when any composition within this field is heated. Similarly,B and C are primary phases in their respective primary fields, Baec and Caeb. 

In the region of high content of SiOy, the calculation of the phase equilibrium fails as the formation of two liquids is not considered in the thermodynamic model of silicate melts. This is also the reason for the enlarged liquidus surface of CaTiSiOs up to the high content of silica. 

The liquidus surface of the Cu-Fe-Nb system was not studied experimentally. Thermodynamic calculation [2000Wan] results in a miscibility gap in the liquid state, the thermodynamic parameters being evaluated on the basis of own experimental results. 

The schematic liquidus surface shown in Fig. 3 in the present assessment is constracted speculatively basing on the invariant equilibria in the Cu-Fe-Nb system (Fig. 2). There are two liquid phases in the system. The liquid phase bordering with (Nb) is denoted as L and the liquid phase near die Cu comer is denoted as L . Two critical points, Ci and C2, exist on the monovariant line outlining die miscibility gap where the L + L field contacts with L -1- (Nb) and L -t- e fields, respectively. As indicated by [2002Rag], temperatiues of Ci and C2 are about 1700°C. 

Sch2] Chemical analysis of compositions of two liquid layers after exposition at certain temperatures and quenching. Tammann furnace, graphite crucibles, electrolytic Fe and Cu. Thermodynamic calculation The liquidus surfaces with the miscibility gap and liquidus isotherms. The melting equilibria in stable and metastable systems. 

BUC] Liquidus surface, y-liquid equilibria 1400-1520°C, <40 mass% Ni, <5 mass% C... 

Numerous investigations have been done regarding the liquidus surface, die isothermal sections and the vertical sections in the stable and metastable systems. The other investigations on die ternary system concern the solubility measurements of carbon in the "y and liquid phases which go always widi activity measme-ments, the determination of the phase diagram under high pressures and die kinetics studies of die austenite transformation in martensite or bainite because these phases are important in die forecast of mechanical properties of steel. The main experimental investigations on crystal structure, phase equilibria and thermodynamics are gathered in Table 1. 

The liquidus surface projection of the partial Fe-Fc3C-WC-W system consfructed by [1968Jel] contradicts to the constitution of die currently accepted binary systems. In particular, die W2C phase is presented by one modification the Fc3C phase is shown as stable invariant equilibrium widi the participation of the liquid, (6Fe) and the p phase in die Fe-W system is presented as the eutectic one taking place at 1520°C, and the corresponding invariant point is shifted towards the timgsten side. Stracture formation of die C-Fe-W alloys... 

Consider a temperature midway between the melting points of the pure components and the three eutectic temperatures in system ABC, as shown in Figure 17.34. An isothermal plane at this temperature will cut through all three liquidus surfaces. Near each apex, the plane lies below each liquidus surface, so it shows an area of solid plus liquid filled with tie-lines. In the center of the diagram, the plane is everywhere above the liquidus surfaces, and so it shows a blank field of liquid. Sections at successively lower temperatures would show the two-phase fields expanding and coalescing, leaving smaller and smaller liquid fields. 

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