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| Longauerová M., Fedorová M., Longauer S., Kadlec J., Bořuta J., Fujda M., Janák G., Vojtko M. |
| HETEROGENEITIES OF CHEMICAL COMPOSITON IN CAST PRODUCTS |
| Keywords: Slabs|surface segregation|structure heterogeneities|centreline noncompactibilities|round blooms|central segregation| |
| No 1 (2007), p. 17-25 |
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| Drápala J., Morávková Z., Vrbický J., Dostál V., Sidorov E.V. |
| THE THEORETICAL ASPECTS OF CRYSTALLIZATION IN TERNARY ALLOYS AND THE CHARACTER OF SEGREGATION PROCESSES AT EQUILIBRIUM AND NON-EQUILIBRIUM SOLIDIFICAT |
Abstract
Equilibrium data presented as liquidus and solidus projections are often used to study solidification sequences. In order to make the full use of such projections, information is also required on the solid state composition of a given system at the completion of solidification. Primary phase fields and curves on a liquidus projection as well as the equilibrium and non-equilibrium solidification of ternary alloys are described in this paper. Segregation coefficients of components in ternary systems are very important for prediction of macro- and micro-inhomogeneities in real structures of crystals. Distribution of components in ternary systems after equilibrium and non-equilibrium crystallization is presented in the figures and tables.
Crystallization of alloys in various areas of binary, ternary and/or multicomponent systems can proceed under equilibrium, quasi-equilibrium or non-equilibrium conditions. Crystallization process consists of the decomposition of melt and interaction of primary crystals with coexisting melt. The decomposition proceeds due to the diffusion transfer of mass in the liquid phase. The interaction is determined by the mass transfer between the melt and crystal as well as in the crystal itself.
Behaviour of individual elements at equilibrium crystallization in dependence on the alloy chemical composition is discussed on an example of a ternary system with ideal solubility. Segregation coefficients also take different values. A segregation coefficient of the alloy selected component can even change from the values ko < 1 to the values ko > 1. This is presented in table 1 on the example of the ternary system copper–manganese–nickel for the segregation coefficients of copper.
The distribution of components in the crystal after non-equilibrium crystallization is documented graphically in Fig. 5. A trajectory of the change of chemical composition in the ternary system A-B-C with ideal solubility in both the solid and liquid phase at the non-equilibrium crystallization of the alloy is drawn in Fig.6.
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| Keywords: ternary system|crystallization|liquidus|solidus|segregation coefficient| |
| No 1 (2007), p. 76-84 |
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