Phase Diagrams Aisling Coughlan 1 Phase Equilibria Solubility Limit Introduction Solutions Mixtures Sucrose Water Phase Diagram Solubility Limit Answer 65 wt sugar If Co 65 wt sugar syrup If Co 65 wt sugar syrup sugar L liquid 60 L 40 liquid solution i e syrup 20 0 S solid sugar 20 40 6065 80 100 Co Composition wt sugar Pure Sugar solubility limit at 20 C Solubility Limit 80 Pure Water Question What is the 100 Temperature C Max concentration for which only a single phase solution occurs 2 Components and Phases 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 a and b AluminumCopper Alloy b lighter phase a darker phase 3 Effect of T Composition Co Changing T can change of phases Changing Co can change of phases B 100 C 70 D 100 C 90 1 phase watersugar system Temperature C 100 2 phases L 80 liquid 60 L liquid solution 40 i e syrup S solid sugar A 20 C 70 20 2 phases 0 0 20 40 60 70 80 100 Co Composition wt sugar 4 Phase Equilibria Simple solution system e g Ni Cu solution 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 Ni and Cu are totally miscible in all proportions 5 Phase Diagrams Indicate phases as function of T Co and P For this course binary systems just 2 components independent variables T and Co T C Phase Diagram for Cu Ni system 2 phases 1600 1500 L liquid 3 phase fields 1400 1300 a FCC solid solution 1200 1100 1000 0 20 40 60 80 100 wt Ni 6 Phase Diagrams and types of phases Rule 1 T C 1600 B 1250 C 35 L liquid 1500 Examples A 1100 C 60 1 phase a B 1250 C 35 2 phases L a 1400 1300 1200 1100 1000 Cu Ni phase diagram a FCC solid solution A 1100 C 60 0 20 40 60 80 100 wt Ni 7 Phase Diagrams composition of phases Rule 2 Examples T C Cu Ni system A TA Co 35 wt Ni 1300 L liquid At T A 1320 C Only Liquid L B TB CL Co 35 wt Ni At T D 1190 C 1200 D Only Solid a TD Ca Co 35 wt Ni 20 3032 35 At T B 1250 C CLCo Both a and L CL C liquidus 32 wt Ni here Ca C solidus 43 wt Ni here tie line a solid 4043 50 Ca wt Ni 8 Phase Diagrams weight fractions of phases Rule 3 Examples Co 35 wt Ni At T A Only Liquid L W L 100 wt W a 0 At T D Only Solid a W L 0 Wa 100 wt At T B Both a and L WL 43 35 S 73 wt R S 43 32 Wa R 27 wt R S Cu Ni system T C A TA 1300 TB 1200 TD 20 tie line L liquid B R S D 3032 35 CLCo a solid 40 43 50 Ca wt Ni 9 The Lever Rule Tie line connects the phases in equilibrium with each other essentially an isotherm T C How much of each phase Think of it as a lever teeter totter tie line 1300 L liquid B TB a solid 1200 R 20 Ma ML S 30C C 40 C a L o R 50 S M a S M L R wt Ni WL C C0 ML S a ML Ma R S Ca CL Wa C CL R 0 R S Ca CL 10 Ex Cooling in a Cu Ni Binary Phase diagram Cu Ni system System is binary i e 2 components Cu and Ni T C L liquid 130 0 L 35 wt Ni a 46 wt Ni L 35wt Ni A 35 32 Co 35 wt Ni 110 0 20 46 43 L 32 wt Ni 36 120 0 Consider B C D 24 isomorphous i e complete solubility of one component in another a phase field extends from 0 to 100 wt Ni Cu Ni system a 43 wt Ni E L 24 wt Ni a 36 wt Ni a solid 30 35 Co 40 50 wt Ni 11 Cored vs Equilibrium Phases Ca changes as we solidify Cu Ni case First a to solidify has Ca 46 wt Ni Last a to solidify has Ca 35 wt Ni Fast rate of cooling Cored structure Slow rate of cooling Equilibrium structure First a to solidify 46 wt Ni Last a to solidify 35 wt Ni Uniform C a 35 wt Ni 12 Mechanical Properties Cu Ni System Effect of solid solution strengthening on Ductility EL AR 400 TS for pure Ni 300 TS for pure Cu 200 0 20 40 Cu 60 80 100 Ni Composition wt Ni Peak as a function of Co Elongation EL Tensile Strength MPa Tensile strength TS 60 EL for pure Cu EL for pure Ni 50 40 30 20 0 20 Cu 40 60 80 100 Ni Composition wt Ni Min as a function of Co 13 Binary Eutectic Systems Cu Ag system T C Ex Cu Ag system 1200 3 single phase regions L liquid 1000 L a b a L a 779 C Limited solubility L b b 800 T a mostly Cu 8 0 71 9 91 2 E b mostly Ag 600 TE No liquid below TE a b 400 CE Min melting TE composition 200 Eutectic transition L CE 0 a CaE b CbE 20 40 60 CE 80 100 Co wt Ag 14 EX Pb Sn Eutectic System 1 For a 40 wt Sn 60 wt Pb alloy at 150 C find the phases present a b T C compositions of phases CO 40 wt Sn Ca 11 wt Sn Cb 99 wt Sn the relative amount of each phase Wa C CO S b R S Cb Ca Pb Sn system 300 200 L liquid a L a 18 3 150 100 99 40 59 67 wt 99 11 88 C Ca Wb R O Cb Ca R S L b b 183 C 61 9 R 97 8 S a b 40 11 29 33 wt 99 11 88 0 11 20 Ca 40 Co 60 80 C wt Sn 99100 Cb 15 EX Pb Sn Eutectic System 2 For a 40 wt Sn 60 wt Pb alloy at 200 C find the phases present a L T C compositions of phases CO 40 wt Sn Ca 17 wt Sn CL 46 wt Sn the relative amount of each phase CL CO 46 40 Wa CL Ca 46 17 6 21 wt 29 Pb Sn system 300 a 220 200 L a R L liquid L b b S 183 C 100 CO Ca 23 WL 79 wt CL Ca 29 a b 0 17 20 Ca 40 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