DOCSLIB.ORG

Phase Diagrams [9]

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text

Load more

Phase Diagrams [9] Cu-Ag phase diagram Brazil’s map 1> Some important definitions… • Component - chemically recognizable species (Fe and C in carbon steel, H2O and NaCl in salted water). A binary alloy contains two components, a ternary alloy – three, etc. • Phase – a portion of a system that has uniform physical and chemical characteristics. Two distinct phases in a system have distinct physical or chemical characteristics (e.g. water and ice) and are separated from each other by definite phase boundaries. A phase may contain one or more components. • A single-phase system is called homogeneous, systems with two or more phases are mixtures or heterogeneous systems. • Solvent - host or major component in solution. • Solute - minor component 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 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. 2> Some important definitions… ¾ Solubility Limit: after Callister & Rethwisch (2014) 3> Some important definitions… • Microstructure: The properties of an alloy depend not only on proportions of the phases but also on how they are arranged structurally at the microscopic level. Thus, the microstructure is specified by the number of phases, their proportions, and their arrangement in space. matrix graphite This is an alloy of Fe with 4 wt.% C. There are several phases. The long gray regions are flakes of graphite. The matrix is a fine mixture of BCC Fe and Fe3C compound. 4> Some important definitions… • Equilibrium – thermodynamic state where a system is stable at constant temperature, pressure and composition, not changing with time. 5> Gibb’s Phase Rule ¾ A tool to define the number of phases and/or degrees of phase changes that can be found in a system at equilibrium P + F = C + N P: # of phases present F: degrees of freedom (temp., pressure, composition) C: components or compounds N: noncompositional variables (usually 1) For the Cu-Ag system @ 1 atm for a single phase P: N=1 (temperature), C = 2 (Cu-Ag), P= 1 (a, b, L) F = 2 + 1 – 1= 2 This means that to characterize the alloy within a single phase field, 2 parameters must be given: temperature and composition. If 2 phases coexist, for example, α+L , β+L, α+β, then according to GPR, we have 1 degree of freedom: F = 2 + 1 – 2= 1. So, if we have temperature or composition, then we can completely define the system. If 3 phases exist (for a binary system), there are 0 degrees of freedom. This means the composition and temperature are fixed. This condition is met for a eutectic system by the eutectic isotherm. 6> Unary phase diagram water pure iron 7> Binary Systems ¾ Binary Isomorphous Systems: An alloy system that contains two components that attain complete liquid and solid solubility of the components, e.g. Cu and Ni alloy. It is the simplest binary system Crystal Electro- r (nm) Structure negativity 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. 8> Cu-Ni Isomorphous phase diagram Information: ¾ Phases, ¾ Compositions, ¾ Weight fractions. Lever Rule 9> Determination of phase(s) present ¾ Rule 1: If we know T and Co, then we know: - which phase(s) is (are) present. T(ºC) •Examples: 1600 A (1100ºC, 60 wt% Ni): L (liquid) 1 phase: α 1500 dus Cu-Ni ui 1400 liq phase B (1250ºC, 35 wt% Ni): us id 2 phases: L + α ol diagram α s 1300 (1250ºC,35) + α B L (FCC solid 1200 solution) 1100 A(1100ºC,60) 1000 0 20 40 60 80 100 wt% Ni 10> Determination of phase compositions ¾ Rule 2: If we know T and C0, then we can determine: - the composition of each phase. Cu-Ni system •Examples: T(ºC) T A Consider C0 = 35 wt% Ni A tie line dus qui 1300 L (liquid) li At TA = 1320ºC: + α Only Liquid (L) present L B us T olid CL = C0 ( = 35 wt% Ni) B s α α At TD = 1190ºC: + 1200 L D (solid) Only Solid (α) present TD Cα = C0 ( = 35 wt% Ni) 20 303235 4043 50 At TB = 1250ºC: CL C0 Cα wt% Ni Both α and L present CL = Cliquidus ( = 32 wt% Ni) Cα = Csolidus ( = 43 wt% Ni) 11> Determination of phase weight fractions ¾ Rule 3: If we know T and C0, then can determine: - the weight fraction of each phase. Cu-Ni •Examples: T(ºC) system Consider C = 35 wt% Ni A 0 T tie line s A idu iqu At TA : Only Liquid (L) present 1300 L (liquid) l + α WL = 1.00, Wα = 0 L B us T olid At TD : Only Solid ( α) present B R S s α WL = 0, Wα = 1.00 + α 1200 L (solid) At T :Both and L present D B α TD S 43− 35 20 303235 4043 50 WL = = 0= . 73 R +S 43− 32 CLC0 Cα wt% Ni R W = = 0.27 α R +S 12> The Lever Rule: A Proof ¾ Sum of weight fractions: W L + Wα = 1 ¾ Conservation of mass: C o = WLCL + WαCα ¾ Combine above equations: C − C S C − C R W = α o = W o L = L + α = + Cα − CL R S Cα − CL R S • A geometric interpretation: moment equilibrium: CL Co Cα W R = W S R S L α WL Wα 1 − Wα solving gives Lever Rule 13> Development of the microstructure ¾ Solidification in the solid + liquid phase occurs gradually upon cooling from the liquidus line. ¾ The equilibrium composition of the solid and the liquid change gradually during cooling (as can be determined by the tie-line method.) ¾ Nuclei of the solid phase form and they grow to consume all the liquid at the solidus line. 14> Development of the microstructure When cooling is too fast for atoms to diffuse and produce equilibrium conditions, nonequilibrium concentrations are produced. The nonuniform composition produced by nonequilibrium solidification is known as segregation. Microsegregation can cause hot shortness which is the melting of the material below the melting point of the equilibrium solidus. Homogenization, which involves heating the material just below the non-equilibrium solidus and holding it there for a few hours, reduces the microsegregation by enabling diffusion to bring the composition back to equilibrium. 15> Cored vs Equilibrium Structures • Cα changes as we solidify. • Cu-Ni case: First α to solidify has Cα = 46 wt% Ni. Last α to solidify has Cα = 35 wt% Ni. • Slow rate of cooling: • Fast rate of cooling: Equilibrium structure Cored structure Uniform Cα: 35 wt% Ni First α to solidify: 46 wt% Ni Last α to solidify: < 35 wt% Ni 16> Mechanical Properties of the Cu-Ni System ¾ Effect of solid solution strengthening on: 17> Three-phase Reactions in Phase Diagrams 18> Eutectoid & Peritectic Peritectic transition γ + L δ ¾ Cu-Zn Phase diagram: Eutectoid transition δγ+ ε 19> Intermetallic Compounds Mg2Pb Note: an intermetallic compound forms a line - not an area - because stoichiometry (i.e. composition) is exact. 20> Microstructures in Eutectic Systems Pb-Sn system cooling ( 61 . 9 wt% Sn) L (1α 8 .3 wt%+ β Sn) ( 9 7.8 wt% Sn) heating 21> Lamellar Eutectic Structure ¾A 2-phase microstructure resulting from the solidification of a liquid having the eutectic composition where the phases exist as a lamellae Pb‐rich that alternate with one another. ¾Formation of eutectic Sn‐rich layered microstructure in the Pb-Sn system during solidification at the eutectic composition. Compositions of α and β phases are very different. Solidification involves redistribution of Pb and Sn atoms by atomic diffusion. 22> Hypoeutectic & Hypereutectic Compositions 300 L T(°C) L+α 200 α L+β β TE (Pb-Sn α + β System) 100 0 20 40 60 80 100 Co, wt% Sn eutectic hypoeutectic: Co = 50 wt% Sn 61.9 hypereutectic: (illustration only) eutectic: C =61.9wt% Sn α o β α β α α β β α β α β 175 μm 160 μm eutectic micro-constituent 23> Iron-Carbon (Fe-C) Phase Diagram • 2 important T(°C) Max. C solubility in γ iron = 2.11 wt% 1600 points δ -Eutectic (A): 1400 L L ⇒γ+ Fe C 3 γ γ+L 1200 A L+Fe C -Eutectoid (B): (austenite) 1148°C 3 R S γ⇒α+Fe3C 1000 γγ γ+Fe3C α γ γ + 800α γ B 727°C = Teutectoid R S C (cementite) 3 600 α+Fe C 3 Fe 400 0 1234566.7 (Fe) 0.76 4.30 120 μm Co, wt% C Result: Pearlite = Fe3C (cementite-hard) alternating layers of α (ferrite-soft) α and Fe3C phases eutectoid C 24> Iron-Carbon (Fe-C) Phase Diagram Hypoeutectoid Steel T(°C) 1600 δ 1400 L (Fe-C System) γγ γ γ+L γ γ 1200 1148°C L+Fe C (austenite) 3 γ γ 1000 γ γ γ +Fe3C α 800 r s αγ γ 727°C α γ γ R S C (cementite) α 3 wα =s/(r+s) 600 α+Fe C wγ =(1- wα) 3 Fe 400 0 1234566.7 α (Fe) C0 Co, wt% C pearlite 0.76 w pearlite = wγ Hypoeutectoid 100 μm wα =S/(R+S) steel w =(1-w ) Fe3C α pearlite proeutectoid ferrite 25> Iron-Carbon (Fe-C) Phase Diagram T(°C) Hypereutectoid Steel 1600 δ 1400 L (Fe-C System) γ γ γ γ+L 1200 1148°C L+Fe C γ γ (austenite) 3 γ γ 1000 γ γ γ +Fe3C Fe C 3 s γ γ 800 r γ γ C (cementite) α R S 3 600 wFe C =r/(r+s) α +Fe C 3 3 Fe wγ =(1-w Fe C) 3 400 0 1234566.7Co (Fe) C , wt%C pearlite 0.76 o w pearlite = wγ wα =S/(R+S) Hypereutectoid w =(1-w α) 60 μm Fe3C steel pearlite proeutectoid Fe3C 26> Application of the Lever Rule (I) Example: For a AISI 1040 carbon steel (0.40 wt% C) at a temperature just below the eutectoid, determine the following: a) composition of cementite (Fe3C) and ferrite (α) b) the amount of carbide (cementite) in grams that forms per 100 g of steel c) the amount of pearlite and proeutectoid ferrite (α) 27> Application of the Lever Rule (I) ¾ Solution: CO = 0.40 wt% C C = 0.022 wt% C a) composition of Fe C and ferrite (α) α 3 C = 6.70 wt% C Fe3 C b) the amount of carbide (cementite) in grams that forms per 100 g of steel 1600 δ Fe3 C CCo − α = x 100 1400 L Fe+ C αCC− T(°C) 3 Fe3 C α γ+L 1200 γ L+Fe C 0 .
Recommended publications
  • Phase Diagrams

    Phase Diagrams

    Module-07 Phase Diagrams Contents 1) Equilibrium phase diagrams, Particle strengthening by precipitation and precipitation reactions 2) Kinetics of nucleation and growth 3) The iron-carbon system, phase transformations 4) Transformation rate effects and TTT diagrams, Microstructure and property changes in iron- carbon system Mixtures – Solutions – Phases Almost all materials have more than one phase in them. Thus engineering materials attain their special properties. Macroscopic basic unit of a material is called component. It refers to a independent chemical species. The components of a system may be elements, ions or compounds. A phase can be defined as a homogeneous portion of a system that has uniform physical and chemical characteristics i.e. it is a physically distinct from other phases, chemically homogeneous and mechanically separable portion of a system. A component can exist in many phases. E.g.: Water exists as ice, liquid water, and water vapor. Carbon exists as graphite and diamond. Mixtures – Solutions – Phases (contd…) When two phases are present in a system, it is not necessary that there be a difference in both physical and chemical properties; a disparity in one or the other set of properties is sufficient. A solution (liquid or solid) is phase with more than one component; a mixture is a material with more than one phase. Solute (minor component of two in a solution) does not change the structural pattern of the solvent, and the composition of any solution can be varied. In mixtures, there are different phases, each with its own atomic arrangement. It is possible to have a mixture of two different solutions! Gibbs phase rule In a system under a set of conditions, number of phases (P) exist can be related to the number of components (C) and degrees of freedom (F) by Gibbs phase rule.
  • Chapter 9. Phase Diagrams

    Chapter 9. Phase Diagrams

    Chapter 9. Phase Diagrams 9.1 Introduction Good understanding of phase diagrams will help engineers to design and control heat treatment procedures:- some properties of materials are functions of their microstructures, and hence of their thermal histories. The development of microstructure of an alloy is related to the characteristics of its phase diagram. Phase diagrams provide valuable information about melting, casting, crystallization, and other phenomenon. Topics to be discussed are: terminology of phase diagrams and phase transformations, interpretation of phase, simple binary phase diagrams, and development of equilibrium microstructures upon cooling. DEFINITIONS AND BASIC CONCEPTS “Components”: pure metals and/or compounds of which an alloy is composed (Ex.: solute and solvent in Cu-Zn brass). A “System”: a specific body of material under consideration (Ex.: ladle of molten steel) or a series of alloys consisting of the same components but without regard to alloy composition (Ex.: the iron- carbon system). “Solid solution”: consists of atoms of at least two different types; the solute atoms (minor component) occupy either substitutional or interstitial positions in the solvent lattice (host or major component). 9.2 Solubility Limit Solubility limit is the maximum concentration of solute atoms that may dissolve in the solvent to form a solid solution at a specific temperature. Adding more solute in excess of this limit results in forming another solid solution or compound with different composition. Consider sugar-water (C12H22O11 – H2O) system. As sugar is added to water Æ sugar-water solution (syrup). Adding more sugar Æ solution becomes more concentrated until solubility limit is reached (solution is saturated with sugar).
  • Binary Solutions with Unlimited Solubility

    Binary Solutions with Unlimited Solubility

    Diffusion and Kinetics Lecture: Binary phase diagrams and Gibbs free energy curves Nikolai V. Priezjev Textbook: Phase transformations in metals and alloys (Third Edition), By: Porter, Easterling, and Sherif (CRC Press, 2009). Binary phase diagrams and Gibbs free energy curves • Binary solutions with unlimited solubility • Relative proportion of phases (tie lines and the lever principle) • Development of microstructure in isomorphous alloys • Binary eutectic systems (limited solid solubility) • Solid state reactions (eutectoid, peritectoid reactions) • Binary systems with intermediate phases/compounds • The iron-carbon system (steel and cast iron) • Temperature dependence of solubility • Equilibrium vacancy concentration • Three-component (ternary) phase diagrams Reading: Chapter 1.5 of Porter, Easterling, Sherif https://www.slideshare.net/NikolaiPriezjev Binary phase diagram and Gibbs free energy A binary phase diagram is a temperature - composition map which indicates the equilibrium phases present at a given temperature and composition. The equilibrium state can be found from the Gibbs free energy dependence on temperature and composition. Binary solutions with unlimited solubility (I) Let’s construct a binary phase diagram for the simplest case: A and B components are mutually soluble in any amounts in both solid (isomorphous system) and liquid phases, and form ideal solutions (Hmix = 0). We have 2 phases – liquid and solid. Let’s consider Gibbs free energy curves for the two phases at different T. Binary solutions with unlimited solubility (II) Binary solutions with unlimited solubility (III) sol liq A A sol liq B B Binary solutions with unlimited solubility (IV) At T4 and below this temperature the Gibbs free energy of the solid phase is lower than the G of the liquid phase in the whole range of compositions – the solid phase is the only stable phase.
  • Chapter 8 Phase Diagrams

    Chapter 8 Phase Diagrams

    Chapter 8 Phase Diagrams A phase in a material is a region that differ in its microstructure and or composition from another region Al2CuMg Al H2O(solid, ice) in H2O (liquid) ⇒ 2 phases • homogeneous in crystal structure and atomic arrangement • have same chemical and physical properties throughout • have a definite interface and able to be mechanically separated from its surroundings Chapter 8 in Smith & Hashemi Additional resources: Callister, chapter 9 and 10 Chapter 8 1 Phase diagram and “degrees of freedom” A phase diagrams is a type of graph used to show the equilibrium conditions between the thermodynamically-distinct phases; or to show what phases are present in the material system at various T, p, and compositions • “equilibrium” is important: phase diagrams are determined by using slow cooling conditions ⇒ no information about kinetics Degree of freedom (or variance) F is the number of variables (T, p, and composition) that can be changed independently without changing the phases of the system Phase diagram of CO2 Chapter 8 2 8.1 Phase Diagram of Water 3 phases: solid, liquid, vapour Triple point: 4.579 Torr (~603Pa), 0.0098oC • Field – 1 phase • Line – phase coexistence, 2 phases • Triple point – 3 phases Chapter 8 3 8.2 Gibbs Phase Rule Gibbs' phase rule describes the possible # of degrees of freedom (F) in a closed system at equilibrium, in terms of the number of separate phases (P) and the number of chemical components (C) in the system (derived from thermodynamic principles by Josiah W. Gibbs in the 1870s) F + P = C + 2
  • PHASE DIAGRAMS • Also Called Equilibrium Or Constitutional Diagrams • Plots of Temperature Vs

    PHASE DIAGRAMS • Also Called Equilibrium Or Constitutional Diagrams • Plots of Temperature Vs

    Phase Equilibria Reading: West 7 433 PHASE DIAGRAMS • Also called equilibrium or constitutional diagrams • Plots of temperature vs. pressure, or T or P vs. composition, showing relative quantities of phases at equilibrium • Pressure influences phase structure – Remains virtually constant in most applications – Most solid-state phase diagrams are at 1 atm • Note: metastable phases do not appear on equilibrium phase Fe–Fe3C diagrams phase diagram 434 PHASES A phase is a homogeneous portion of a system with uniform physical and chemical characteristics, in principle separable from the rest of the system. A difference in either physical or chemical properties constitutes a phase gaseous state • seemingly only one phase occurs (gases always mix) liquid state • often only one phase occurs (homogeneous solutions) e.g., salt water, molten Na2O-SiO2 • two immiscible liquids (or liquid mixtures) count as two phases solid state • crystalline phases: e.g., ZnO and SiO2 = two phases • polymorphs: e.g., wurtzite and sphalerite ZnS are different phases • solid solutions = one phase (e.g., Al O -Cr O solutions) 2 3 2 3 435 PHASE EQUILIBRIA The equilibrium phase is always the one with the lowest free energy G = H – TS Equilibrium → state with The driving force for a phase minimum free energy under some change is the minimization of free specified combination of energy temperature, pressure, and composition e.g., melting unstable G metastable equilibrium state 436 GIBBS PHASE RULE “On the Equilibrium of Heterogeneous Substances” 1874-78 P + F = C + 2 F = C – P + 2 P: number of phases present at equilibrium Gibbs C: number of components needed to describe the system F: number of degrees of freedom, e.g.

  • Phase Diagrams

    CHAPTER 3 PHASE DIAGRAMS 3.1 MOTIVATION One of the most powerful tools for studying the development of microstruc- ture is the equilibrium phase diagram. A phase diagram embodies infor- mation derived from the thermodynamic principles described in Chap. 2, specialized for a particular range of compositions and presented in a form that makes the data readily accessible. The diagram shows the phases present in equilibrium, as well as the composition of the phases over a range of temperatures and pressures. In this text, we will not normally be concerned with the effect of pressure on thermodynamic equilibrium as we will work almost entirely with condensed phases (solids and liquids) in systems open to the atmosphere. We will thus for the most part assume that the pressure is constant. Before we begin, it should be noted that thermodynamics tells us what should happen, i.e., it identifies the lowest energy configuration. How- ever, as already stated in Chap. 2, it does not guarantee that that is what will happen, as the behavior of the real system may be constrained by ki- netic processes, such as solute or heat transport. Nevertheless, we will frequently make the assumption that there is sufficient time for these pro- cesses to establish local thermodynamic equilibrium at the solid-liquid in- terface, if not in the entire system. This will allow us to use the infor- mation in equilibrium phase diagrams, even in cases where transport is incomplete. The present chapter provides some fundamental concepts and tools for analyzing phase diagrams building upon the basics of thermodynam- ics and deviations from equilibrium that were presented in Chap.
  • Eutectic Systems • the Simplest Kind of System with Two Solid Phases Is Called a Eutectic System

    Eutectic Systems • the Simplest Kind of System with Two Solid Phases Is Called a Eutectic System

    Eutectic Systems • The simplest kind of system with two solid phases is called a eutectic system. • A eutectic system contains two solid phases at low temperature. These phases may have different crystal structures, or the same crystal structure with different lattice parameters. •Examples: – Pb (FCC) and Sn (tetragonal) - solder systems – Fe (BCC) and C (graphite - hexagonal) -cast irons – Al (FCC) and Si (diamond cubic) - cast aluminum alloys – Cu(FCC) and Ag(FCC) – high temperature solder Cu/Ag Eutectic System • Copper and Silver are both FCC, but their lattice parameters and atomic radii are very different, so they have limited solubility in the solid state. • There are two solid stable phases α and β, and at high temperatures there is a eutectic reaction where the solids α, β and the liquid coexist. ← ⎯⎯Heating⎯ L(CE) α(CαE) + β(CβE) ⎯ Coolin⎯→⎯g Cu – Ag System Cu: α phase Ag: β phase Eutectic means “easily melted” in Greek Point E: invariant point (eutectic point) BG line: isotherm line AB: Solidus line FG: BC: Solvus line GH: AE: Liquidus line EF: BEG: Solidus line, isotherm line TE: eutectic isotherm Eutectic isotherm Invariant or eutectic point Eutectic Reaction: Cooling L(CE) α(CαE) + β(CβE) Heating For copper-silver system: Cooling L(71.9wt%Ag) α(8.0wt%Ag) + β(91.2wt%Ag) Heating Eutectic or invariant point - Liquid and two solid phases co-exist in equilibrium at the eutectic composition CE and the eutectic temperature TE. Eutectic isotherm - horizontal solidus line at TE. Binary Eutectic System Eutectic reaction – transition from liquid to mixture of two solid phases, α + β at eutectic concentration CE.
  • PHASE DIAGRAMS Phase –A Chemically and Structurally Homogenous Region of a Material

    PHASE DIAGRAMS Phase –A Chemically and Structurally Homogenous Region of a Material

    PHASE DIAGRAMS Phase –a chemically and structurally homogenous region of a material. Region of uniform physical and chemical characteristics. Phase boundaries separate two distinct phases. A single phase system is called homogeneous. A system with two or more phases is called heterogeneous. Phase Diagram –a graphic representation showing the phase or phases present for a given composition, temperature and pressure. Component –the chemical elements which make up the alloy. Solvent atoms: primary atomic species. Host atoms Solute atoms: the impurities. Normally the minor component Solubility Limit ‐ Maximum concentration of solute atoms that may dissolve in the solvent to form a solid solution. The excess of solute forms another phase of different composition. Example: water‐sugar Phase Diagrams of Pure Substances •Predicts the stable phase as a function of Ptotal and T. Example: water can exist in solid, liquid and vapor phases, depending on the conditions of temperature and pressure. • Characteristic shape punctuated by unique points. –Phase equilibrium lines –Triple Point (three different phases of water in equilibrium) – Critical Point Example: In the pressure‐temperature (PT) phase diagram of water there exists a triple point at low pressure (4.579 torr) and low temperature (0.0098oC) where solid, liquid and vapor phases of water coexists. Vaporization Line –Liquid and vapor coexists Freezing Line – Liquid and solid coexist. Sublimation Line – Solid and vapor coexist Phase ‐ Any portion including the whole of a system, which is physically homogeneous within it and bounded by a surface so that it is mechanically separable from any other portions. Gibbs Phase Rule From thermodynamic considerations, J.W.
  • Chapter 9: Phase Diagrams ISSUES to ADDRESS

    Chapter 9: Phase Diagrams ISSUES to ADDRESS

    Chapter 9: Phase Diagrams 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? Phase A Phase B Nickel atom Copper atom Chapter 9 - 1 Phase Equilibria: Solubility Limit Introduction – Solutions – solid solutions, single phase – Mixtures – more than one phase Adapted from Fig. 9.1, Callister 7e. Sucrose/Water Phase Diagram • Solubility Limit : 100 Max concentration for Solubility which only a single phase 80 Limit L solution occurs. (liquid) 60 L + Question: What is the 40 (liquid solution S solubility limit at 20°C? i.e., syrup) (solid 20 Temperature (°C) Temperature sugar) Answer: 65 wt% sugar . If C < 65 wt% sugar: syrup o 0 20 40 60 65 80 100 If Co > 65 wt% sugar: syrup + sugar. Co =Composition (wt% sugar) Sugar Pure Pure Water Chapter 9 - 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., α and β). Aluminum- β (lighter Copper phase) Alloy α (darker phase) Adapted from chapter-opening photograph, Chapter 9, Callister 3e. A phase maybe defined as a homogeneous portion of a system that has Chapter 9 - 3 uniform physical and chemical characteristics. Effect of T & Composition ( Co) • Changing T can change # of phases: path A to B.