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MSE 2001

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Material science Phase Equilibria
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  1 Chapter 7 Phase Equilibria and Phase Diagrams ã Introduction ã The one-component phase diagram ã Phase equilibria in a two-component system ã The eutectic phase diagram ã The peritectic phase diagram ã The monotectic phase diagram ã Complex diagrams  2 Phase  A chemically and structurally homogeneous region of a material  A part of a system, physically distinct, macroscopically homogeneous, and of fixed or variable composition. It is mechanically separable from the rest of the system.  A phase is a region within which all the intensive variables vary continuously, whereas at least some of them have discontinuities at the borders between phases. ice water ice + water   2 phases = solid phase + liquid phase I want to drink “2 -phase water consisting of solid phase and liquid phase”.    3 Phase diagram Graphical representation of the combination of temperature, pressure, composition, or other variables for which specific phases exist at equilibrium. Phase diagram of Water (H 2 O) Phase diagram of Carbon dioxide (CO 2 ) State point: a position on the phase diagram   0.47 g/cm 3 @304.25 K & 72.9 atm  4 One-Component Phase Diagrams Gibbs Phase Rule for systems in equilibrium Component: a chemical species whose concentration in a phase can be varied independently of the other species’ concentration  Number of degrees of freedom in equilibrium is the number of variables (p, T, or composition) that can be independently adjusted without disturbing equilibrium. water F = C  – P + 2C-ComponentsP-Number of phasesF-Degrees of freedomF = 2F = 1F = 1 F = 0F = 0 F = 2F = 2
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