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Unformatted text preview: ME 382 Lecture 09 24/ix/07 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 - 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% & 41 wt% liquid 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 phase is 60 wt% Ni & 40 wt% Cu Below 1280 C - Solid is a single phase ( phase) that is a solid solution with a composition of 60 wt% Ni & 40 wt% Cu ME 382 Lecture 09 24/ix/07 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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- Spring '08