Lecture17 - Chapter 9 - 1 ISSUES TO ADDRESS... • When we...

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Unformatted text preview: Chapter 9 - 1 ISSUES TO ADDRESS... • When we combine two elements... what equilibrium state do we get? • In particular, if we specify...--a composition (e.g., wt% Cu - wt% Ni), and--a temperature ( T ) then... How many phases do we get? What is the composition of each phase? How much of each phase do we get? Chapter 9: Phase Diagrams Phase B Phase A Nickel atom Copper atom Chapter 9 - 2 • Components : The elements or compounds which are present in the mixture (e.g., Al and Cu) • Phases : The physically and chemically distinct material regions that result (e.g., α and β ). Aluminum- Copper Alloy Components and Phases α (darker phase) β (lighter phase) Adapted from chapter-opening photograph, Chapter 9, Callister 3e. Chapter 9 - 3 • A phase diagram - graphical representation of the combinations of temperature, pressure, composition, or other variables for which specific phases exist at equilibrium. Chapter 9 - 4 : Min. melting T E 2 components has a special composition with a min. melting T. Adapted from Fig. 9.7, Callister 7e. Binary-Eutectic Systems • Eutectic transition L ( C E ) α ( C α E ) + β ( C β E ) • 3 single phase regions ( L , α,β ) • Limited solubility: α : mostly Cu β : mostly Ag • T E : No liquid below T E • C E composition Ex.: Cu-Ag system Cu-Ag system L (liquid) α L + α L + β β α + β C o , wt% Ag 20 40 60 80 100 200 1200 T (°C) 400 600 800 1000 C E T E 8.0 71.9 91.2 779°C Chapter 9 - 5 L + α L + β α + β 200 T (°C) 18.3 C , wt% Sn 20 60 80 100 300 100 L (liquid) α 183°C 61.9 97.8 β • For a 40 wt% Sn-60 wt% Pb alloy at 150°C, find...--the phases present: Pb-Sn system EX: Pb-Sn Eutectic System (1) α + β--compositions of phases: C O = 40 wt% Sn--the relative amount of each phase: 150 40 C o 11 C α 99 C β S R C α = 11 wt% Sn C β = 99 wt% Sn W α = C β- C O C β- C α = 99 - 40 99 - 11 = 59 88 = 67 wt% S R + S = W β = C O- C α C β- C α = R R + S = 29 88 = 33 wt% = 40 - 11 99 - 11 Adapted from Fig. 9.8, Callister 7e. Chapter 9 - 6 L + β α + β 200 T (°C) C , wt% Sn 20 60 80 100 300 100 L (liquid) α β L + α 183°C • For a 40 wt% Sn-60 wt% Pb alloy at 220°C, find...--the phases present: Pb-Sn system Adapted from Fig. 9.8, Callister 7e. EX: Pb-Sn Eutectic System (2) α + L--compositions of phases: C O = 40 wt% Sn--the relative amount of each phase: W α = C L- C O C L- C α = 46 - 40 46 - 17 = 6 29 = 21 wt% W L = C O- C α C L- C α = 23 29 = 79 wt% 40 C o 46 C L 17 C α 220 S R C α = 17 wt% Sn C L = 46 wt% Sn Chapter 9 - 7 : Min. melting T E 2 components has a special composition with a min. melting T.with a min....
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This note was uploaded on 04/06/2008 for the course MSE 201 taught by Professor Brenner during the Spring '08 term at N.C. State.

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Lecture17 - Chapter 9 - 1 ISSUES TO ADDRESS... • When we...

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