09-3 (1) - Chapter 10 - E45 Lecture 9/25/09 Chapter 10 - 2...

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Unformatted text preview: Chapter 10 - E45 Lecture 9/25/09 Chapter 10 - 2 ISSUES TO ADDRESS... When we combine two elements... what is the resulting equilibrium state? In particular, if we specify...-- the composition (e.g., wt% Cu - wt% Ni), and-- the temperature (T ) then... How many phases form? What is the composition of each phase? What is the amount of each phase? Chapter 10: Phase Diagrams Phase B Phase A Nickel atom Copper atom Phase = physically and chemically distinct material Chapter 10 - 3 Phase Equilibria: Solubility Limit Solution solid, liquid, or gas solutions, single phase Mixture more than one phase Chapter 10 - 4 Phase Equilibria: Solubility Limit Solution solid, liquid, or gas solutions, single phase Mixture more than one phase Solubility Limit : Maximum concentration for which only a single phase solution exists. Sugar/Water Phase Diagram Sugar Temperature (C) 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. 10.1, Callister & Rethwisch 3e. Chapter 10 - 5 Phase Equilibria: Solubility Limit Solution solid, liquid, or gas solutions, single phase Mixture more than one phase Question: What is the solubility limit for sugar in water at 20C ? Answer: 65 wt% sugar . At 20C, if C < 65 wt% sugar: syrup At 20C, if C > 65 wt% sugar: syrup + sugar 65 Solubility Limit : Maximum concentration for which only a single phase solution exists. Sugar/Water Phase Diagram Sugar Temperature (C) 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. 10.1, Callister & Rethwisch 3e. Chapter 10 - 6 Components : The elements or compounds which are present in the alloy (e.g., Al and Cu) Phases : The physically and chemically distinct material regions that form (e.g., and ). Aluminum- Copper Alloy Components and Phases (darker phase) (lighter phase) Adapted from chapter- opening photograph, Chapter 9, Callister, Materials Science & Engineering: An Introduction, 3e. Chapter 10 - 7 70 80 100 60 40 20 Temperature (C) C = Composition (wt% sugar) L ( liquid solution i.e., syrup) 20 100 40 60 80 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. 10.1, Callister & Rethwisch 3e. D (100C,C = 90) 2 phases B (100C,C = 70) 1 phase A (20C,C = 70) 2 phases Chapter 10 - 8 Criteria for Solid Solubility Crystal Structure electroneg r (nm) Ni FCC 1.9 0.1246 Cu FCC 1.8 0.1278 Both have the same crystal structure (FCC) and have similar electronegativities and atomic radii ( W. Hume Rothery rules ) suggesting high mutual solubility....
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This note was uploaded on 07/05/2010 for the course E 45 taught by Professor Gronsky during the Fall '08 term at University of California, Berkeley.

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09-3 (1) - Chapter 10 - E45 Lecture 9/25/09 Chapter 10 - 2...

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