3Phase Diagram

# 3Phase Diagram - Chapter 9 Phase Diagrams Why Study Phase...

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Chapter 9 - 1 Why Study Phase Diagram? Because there is a strong correlation between microstructures and mechanical properties and the development of microstructures of an alloy is related to the characteristic of its phase diagram Provide valuable information about melting, casting, crystallization and other phenomena Chapter 9: Phase Diagrams

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Chapter 9 - 2 Components : Pure metal and or compound of which alloy is composed (e.g. Cu and Zn) System : a specific body of material under consideration or a series of alloys consisting of the same component ( e.g. iron-carbon system) Solvent : represent the element or compound that is present in the greatest amount Solute : an element or compound present in a minor concentration Phase : a homogeneous portion of a system that is uniform physical and chemical characteristics Definitions
Chapter 9 - 3 Solubility Limit Question: What is the solubility limit for sugar in water at 20ºC ? Answer: 65 wt% sugar . At 20ºC, if C < 65 wt% sugar: syrup At 20ºC, if C > 65 wt% sugar: syrup + sugar 65 Solubility Limit : Maximum concentration of solute atoms that may dissolve in the solvent to form a solid solution Solubility limit depend on temp. Sugar/Water Phase Diagram Sugar Temperature (ºC) 0 20 40 60 80 100 C = Composition (wt% sugar) L (liquid solution i.e., syrup) Solubility Limit L (liquid) + S (solid sugar) 20 40 60 80 100 Water Adapted from Fig. 9.1, Callister & Rethwisch 8e. Solution – solid, liquid, or gas solutions, single phase Mixture – more than one phase

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Chapter 9 - 4 70 80 100 60 40 20 0 Temperature (ºC) C = Composition (wt% sugar) L ( liquid solution i.e., syrup) 20 100 40 60 80 0 L (liquid) + S (solid sugar) Effect of Temperature & Composition Altering T can change # of phases: path A to B . Altering C can change # of phases: path B to D . water- sugar system Adapted from Fig. 9.1, Callister & Rethwisch 8e. D (100ºC, C = 90) 2 phases B (100ºC, C = 70) 1 phase A (20ºC, C = 70) 2 phases
Chapter 9 - 5 Phases Phase : A homogeneous portion of a system that is uniform physical and chemical characteristics Every pure material is considered to be a phase If more than one phase is present in a system each will have its own distinct properties and a boundary separating the phases will exist . Eg. – sugar water solution When two separate phases exists they are physically dissimilar but identical in chemical make up e. Ice – water : solid – liquid Single phase is termed homogeneous Two or more phase : heterogeneous

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Chapter 9 - Microstructure Physical properties in particular mechanical behaviour of material depend on microstructure. In metal alloy microstructure is characterized by the number of phases present, their proportion and the manner in which they are distributed or arrange The microstructure of an alloy depends on alloying elements present, their concentrations and their heat treatment of the alloy 6
Chapter 9 - Phase Equilibria Free energy is a function of the internal energy of a system and the readomness of disorder of the atoms A system is at equilibrium if its free energy is at a minimum

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