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Unformatted text preview: ME 382 Lecture 09 27/ix/10 1 E QUILIBRIUM P HASE D IAGRAMS • Cu / Ni completely soluble in both liquid and solid form • Solubility limits in both phases during melting / solidification Solidus line - indicates solubility limit for freezing / melting solid Liquidus line- indicates solubility limit for freezing / melting liquid • Cool a molten alloy of 60 wt% Ni & 40 wt% Cu: Above 1350 ° C - liquid is 60 wt%Ni & 40 wt% Cu At 1350 ° C - α phase (a solid solution) starts to precipitate with a composition of 74 wt% Ni & 26 wt% Cu Liquid phase is still 60 wt% Ni & 40 wt% Cu At 1320 ° C - Lever rule indicates that the alloy is 59 wt% α & 41 wt% liquid α is 67 wt% Ni % 33 wt% Cu Liquid phase is 50 wt% Ni & 50 wt% Cu At 1280 ° C - Last liquid to freeze is 42 wt % Ni & 58 wt % Cu α phase is 60 wt% Ni & 40 wt% Cu Below 1280 ° C - Solid is a single phase ( α phase) that is a solid solution with a composition of 60 wt% Ni & 40 wt% Cu ME 382 Lecture 09 27/ix/10 2 Note: Assume cooling rates are so slow that there is time for the equilibrium concentration to be formed throughout the solid. During cooling, Ni must diffuses from the Ni-rich regions first formed. Otherwise a non-equilibrium microstructure will form....
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- Solubility, WT