Thermal
Binary Solutions
Composition as a thermodynamic variable Gibbs free energy of binary solutions Entropy of formation and Gibbs free energy of an ideal solution Chemical potential of an ideal solution Regular solutions: Heat of formation of a solution Activity of a component, Henry’s and Raoult’s laws Real solutions: interstitial solid solutions, ordered phases, intermediate phases, compounds Equilibrium in heterogeneous systems Reading: Chapter 1.3 of Porter and Easterling, Chapters 9.5, 9.6, 9.9, 9.10 of Gaskell
MSE 3050, Phase Diagrams and Kinetics, Leonid Zhigilei
Solid Solutions (terminology)
Solid solutions are made of a host (the solvent or matrix) which dissolves the minor component (solute). The ability to dissolve is called solubility. Solvent: in an alloy, the element or compound present in greater amount Solute: in an alloy, the element or compound present in lesser amount Solid Solution: homogeneous maintains crystal structure contains randomly dispersed impurities (substitutional or interstitial) Second Phase: as solute atoms are added, new compounds / structures are formed, or solute forms local precipitates Solubility Limit of a component in a phase is the maximum amount of the component that can be dissolved in it (e.g. alcohol has unlimited solubility in water, sugar has a limited solubility, oil is virtually insoluble). The same concepts apply to solid phases: Cu and Ni are mutually soluble in any amount (unlimited solid solubility), while C has a limited solubility in Fe. Whether the addition of impurities results in formation of solid solution or second phase depends the nature of the impurities, their concentration and temperature, pressure…
MSE 3050, Phase Diagrams and Kinetics, Leonid Zhigilei
Composition as a thermodynamic variable
Real materials are almost always mixtures of different elements rather than pure substances: in addition to T and P, composition is also a variable. To understand conditions for equilibrium and phase
Composition as a thermodynamic variable Gibbs free energy of binary solutions Entropy of formation and Gibbs free energy of an ideal solution Chemical potential of an ideal solution Regular solutions: Heat of formation of a solution Activity of a component, Henry’s and Raoult’s laws Real solutions: interstitial solid solutions, ordered phases, intermediate phases, compounds Equilibrium in heterogeneous systems Reading: Chapter 1.3 of Porter and Easterling, Chapters 9.5, 9.6, 9.9, 9.10 of Gaskell
MSE 3050, Phase Diagrams and Kinetics, Leonid Zhigilei
Solid Solutions (terminology)
Solid solutions are made of a host (the solvent or matrix) which dissolves the minor component (solute). The ability to dissolve is called solubility. Solvent: in an alloy, the element or compound present in greater amount Solute: in an alloy, the element or compound present in lesser amount Solid Solution: homogeneous maintains crystal structure contains randomly dispersed impurities (substitutional or interstitial) Second Phase: as solute atoms are added, new compounds / structures are formed, or solute forms local precipitates Solubility Limit of a component in a phase is the maximum amount of the component that can be dissolved in it (e.g. alcohol has unlimited solubility in water, sugar has a limited solubility, oil is virtually insoluble). The same concepts apply to solid phases: Cu and Ni are mutually soluble in any amount (unlimited solid solubility), while C has a limited solubility in Fe. Whether the addition of impurities results in formation of solid solution or second phase depends the nature of the impurities, their concentration and temperature, pressure…
MSE 3050, Phase Diagrams and Kinetics, Leonid Zhigilei
Composition as a thermodynamic variable
Real materials are almost always mixtures of different elements rather than pure substances: in addition to T and P, composition is also a variable. To understand conditions for equilibrium and phase