Browsing by Author "Mamta Saroch"

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Estimation of the heat of fusion of a eutectic mixture from phase diagram data
(1992) P. Ramachandrarao; K.S. Dubey; Mamta Saroch
Simple methods are presented for the estimation of the heat of fusion of a eutectic mixture from the entropy of formation of constituent phases with the aid of data obtainable from the binary phase diagrams. The suggested methods do not require any thermodynamic information concerning the terminal solid solutions if any one of them has negligible solid solubility. In such cases the present methods also do not require thermodynamic information concerning the liquid phase. The procedures are tested with respect to a number of eutectic systems based on simple metals and intermetallic compounds. Results obtained are in excellent agreement with values obtained from direct experiments.
On the composition dependence of faceting behaviour of primary phases during solidification
(1993) Mamta Saroch; K.S. Dubey; P. Ramachandrarao
The entropy of solution of the primary aluminium-rich phase in the aluminium-tin melts has been evaluated as a function of temperature using available thermodynamic and phase equilibria data with a view to understand the faceting behaviour of this phase. It was noticed that the range of compositions in which alloys of aluminium and tin yield a faceted primary phase is correlated with the domain of compositions over which the entropy of solution shows a strong temperature dependence. It is demonstrated that both a high value of the entropy of solution and a strong temperature dependence of it are essential for providing faceting. A strong temperature dependence of the entropy of solution is in turn a consequence of negligible liquidus slope and existence of retrograde solubility. The AgBi and AgPb systems have similar features. © 1993.