Cotectic line

Let us examine the crystallization process of an initial composition Cl the first crystals to form are those of the pure component 2 (y", T = 1175 °C). Crystallization of y" drives the residual liquid radially away from corner 2 along direction 2-Cl, until peritectic curve PP is reached. Here, crystals y" react with the liquid and are transformed into intermediate compound C . Displacement along the peritectic curve terminates when all phase y" is completely resorbed. This occurs geometrically when trajectory C-Cl encounters peritectic curve PP. Crystallization of Cj then proceeds, while the residual liquid moves radially away from C . The liquid path then reaches cotectic curve E -Em and crystals y begin to precipitate in conjunction with Cj. Crystallization continues along the cotectic line and, at ternary eutectic Em, crystals y " precipitate together with C and y until the residual liquid is exhausted. 

Let us now consider the crystallization process operating on a composition C2, initially poorer in component 1 this composition falls into the compositional triangle C -2-3. Crystallization begins in primary phase field y" (T = 1225 °C). Precipitation of y" crystals drives the residual liquid radially away from C2 along direction 2-C2. At T = 1100 °C, the composition of the liquid reaches cotectic line Ejii-P, where crystals y " begin to form together with y". At peritectic point P, crystals y" are partially resorbed by reaction with the liquid to form intermediate compound C . However, the peritectic reaction is not completed, because of ex-... 

Let us now treat compositional relations in the ternary system Di-An-Ab. Figure 7.14A shows the projection of the liquidus surface of the system onto the compositional plane the locations of cotectic line E -E" and of the isotherms are based on the experiments of Bowen (1913), Osborn and Tait (1952), and Schairer and Yoder (1960). 

In Figure 17.32 the cotectic lines and isothermal contours on the liquidus surfaces have been projected onto a plane surface. The triangle is divided by the cotectic lines into three areas, labeled A + L, B-l-L, and C-l-L (where A stands for solid A, etc.), because bulk compositions in these areas will consist of these phases at temperatures below those of the liquidus surfaces. This will... 

Figure 5.4 Phase relations and crystallization paths of Portland cement. Solid lines indicate phase boundaries dashed lines indicate cotectic lines between primary...

Figure 3.26 Cotectic (compatibility) triangles (solid lines) in the ternary diagram Ca0-Al203-Si02 (mass%). In the Si02-rich portion, three important triple points are indicated at the intersection of the phase boundaries (dashed lines). The arrows show the direction of falling temperatures according to the Alkemade theorem...

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