Chapter 9: Phase Diagrams

Transcription

1 hpter 9: Phse Digrms ISSUES TO ADDRESS... oncepts of Phse, omponent, Equilibrium Phse digrm In prticulr, if we specify composition (e.g., wt% u - wt% Ni), nd -- temperture (T) then... How mny phses do we get? Wht is the composition of ech phse? How much of ech phse do we get? Phse A Phse B Nickel tom opper tom hpter 9-1

2 Phses & omponents Phse A homogeneous portion of mterils system tht hs uniform physicl nd chemicl chrcteristics Pure liquid wter: single phse system Pure iced wter: two-phse system - ice nd wter Sugry wter: single phse system - wter with dissolved sugr omponent Pure elements or compounds (e.g., Al nd u) b phse (lighter) Adpted from chpter-opening photogrph, hpter 9, llister 3e. phse (drker) Aluminum-opper Alloy hpter 9-2

3 Imges Illustrting oncepts of Phses & omponents Hl solution 1 phse: liquid Iced Wter 2 phses: liquid nd solid 2 components: wter & Hl 1 component: wter Wter-Oil mixture 2 phses: liquid 1(wtery) & liquid 2 (oily) 2 components: wter & oil / 13/07/oil-nd-wter-do-not-mix/ hpter 9-3

4 lss Exercise For the following system, how mny phses nd how mny components re present? Wht re they Wter with ice cubes in it? Two phses (wter nd ice) nd one component (wter or H2O) Hydrochloric cid solution? One phse (tht uniform solution) nd two components (H2O, Hl) Sugry wter with pure ice cube in it? Two phses (sugry wter nd ice) nd two components (H2O, sugr) ooking oil dropped into cup of wter nd shken up Two phses (oily nd wtery) nd two components (oil nd wter) hpter 9-4

5 Phse Equilibrium Equilibrium: minimum energy stte for system t given T, P, nd composition (i.e. equilibrium stte will persist indefinitely for fixed T, P nd composition). Phse Equilibrium: phse chrcteristics (composition, structure, nd reltive mount) will sty unchnged over time s long s condition (T, P, composition, etc.) do not chnge). Phse digrms digrms bout the existence of equilibrium phses s function of T, P nd composition (Here, often P is kept constnt for simplicity). hpter 9-5

6 Phse Digrm Exmple of Unry System Single component system hpter 9-6

7 Pure Wter Pure Sugr Temperture ( ) Binry (Two omponents) Phse Digrm Temperture oncentrtion Phse(s) Regions: Solution region single phse Mixture region more thn one phse Boundry line represents Solubility imit, i.e., mx concentrtion below which only single phse solution exists Questions: for wter-sugr system wht is the solubility limit t 20? How mny phses when sugr concentrtion below solubility limit? Answer: solubility (limit)~65 wt% sugr If o < 65 wt% sugr: single phse (syrup) If o > 65 wt% sugr: two phses (syrup + solid sugr) Sucrose/Wter Phse Digrm Solubility imit (liquid solution i.e., syrup) Adpted from Fig. 9.1, llister 7e. (liquid) + S (solid sugr) o =omposition (wt% sugr) hpter 9-7

8 Temperture ( ) Effect of T & omposition ( o ) hnging T cn chnge # of phses: hnging o (e.g., by dding more sugr) cn lso chnge # of phses: wtersugr system Adpted from Fig. 9.1, llister 7e ( liquid solution i.e., syrup) pth A to B. pth B to D. B (100,70) 1 phse (liquid) + S (solid sugr) A (20,70) 2 phses D (100,90) 2 phses o =omposition (wt% sugr) hpter 9-8

9 single phse rystl Structure Solid Solution Uniform solution for solid stte mteril (e.g., Ni-u lloy), in which toms mixed rndomly in lttice points, often s electroneg r (nm) Vlence Ni F u F , +2 For Ni-u solid solution lloy, ny tom in lttice site cn be either Ni or u W. Hume Rothery rules Sme crystl structure (e.g., F) Similr electronegtivities Similr tomic rdii Similr vlence stte Ni nd u re totlly miscible in ll proportions nd form continuous single phse solid solution hpter 9-9

10 Binry Phse Digrms for Solid Binry (Isomorphous) System Phse digrm - indicte phses s function of T, o, nd P. under equilibrium condition Binry system: 2 components: u & Ni - independent vribles: T nd (P = 1 tm is lmost lwys used). Phse Digrm for u-ni system T( ) (liquid) (F solid solution) o (wt% Ni) Phses possible: (liquid phse) (F solid solution phse) 3 regions (or fields): (Single phse region) + (Two phse region) (Single phse region) Adpted from Fig. 9.3(), llister 7e. (Fig. 9.3() is dpted from Phse Digrms of Binry Nickel Alloys, P. Nsh (Ed.), ASM Interntionl, Mterils Prk, OH (1991). hpter 9-10

11 Phse Digrms: # nd types of phses t given T, P, & sytem composition If we know T nd o, then we know: --the # nd types of phses present. Exmples: A(1100, 60 wt% Ni): 1 phse: B (1250, 35 wt% Ni): 2 phses: + T( ) (liquid) B (1250,35) (F solid solution) u-ni phse digrm Adpted from Fig. 9.3(), llister 7e. (Fig. 9.3() is dpted from Phse Digrms of Binry Nickel Alloys, P. Nsh (Ed.), ASM Interntionl, Mterils Prk, OH, 1991) A(1100,60) wt% Ni hpter 9-11

12 Phse Digrms: composition of ech of the phses If we know T nd o, then we know: --the composition of ech phse present Exmples: o = 35 wt% Ni At T A = 1320 : Only iquid () phse = o ( = 35 wt% Ni) At T D = 1190 : Only Solid ( ) phse = o ( = 35 wt% Ni ) At T B = 1250 : T( ) T A 1300 T B 1200 T D 20 Both nd phses = liquidus ( = 32 wt% Ni here) = solidus ( = 43 wt% Ni here) (liquid) u-ni system A B D 3235 o tie line (solid) wt% Ni Adpted from Fig. 9.3(b), llister 7e. (Fig. 9.3(b) is dpted from Phse Digrms of Binry Nickel Alloys, P. Nsh (Ed.), ASM Interntionl, Mterils Prk, OH, 1991.) hpter 9-12

13 lss Exercise: omposition of ech phse in phse digrmd For n lloy with 24 wt% Ni, t G (1320 o ), H (1210 o ), I (1160 o ) three points in u-ni phse digrm, give the phse(s) present, nd estimte the composition (in terms of wt% Ni) in ech of the phse(s) u-ni system T( ) o = 24 wt% Ni T G G (liquid) At T G = 1320 : Only iquid () = o = 24 wt% Ni At T I = 1160 : Only Solid ( ) = o = 24 wt% Ni At T H = 1210 : Both nd = liquidus 22 wt% Ni = solidus 32 wt% Ni here 1300 T H 1200 T I 20 H I (solid) wt% Ni Adpted from Fig. 9.3(b), llister 7e. (Fig. 9.3(b) is dpted from Phse Digrms of Binry Nickel Alloys, P. Nsh (Ed.), ASM Interntionl, Mterils Prk, OH, 1991.) hpter 9-13

14 T( ) Reltive Amount of Ech Phse in Two Phse Region - The ever Rule 1300 Tie line connects the phses in equilibrium with ech other under isotherml (sme temperture) condition T B 1200 W 20 (liquid) M M M R wt% Ni Weight frction (in unit of wt%) of the liquid phse B tie line S S R S (solid) o In two phse region, wht is the reltive weight frction (W, in unit of wt%) of ech phse? ever rule 0 Weight of phse Adpted from Fig. 9.3(b), llister 7e. W M M R S R R S S M 0 M R Weight of α phse Weight frction (in unit of wt%) of α solid solution phse hpter 9-14

15 ever Rule: Derivtion Since we hve only 2 phses: W W 1 (1) onservtion of mss requires tht: Amount of Ni in -phse + mount of Ni in liquid phse = totl mount of Ni or (2) W W o From (1), we hve: W 1W Therefore (2) becomes: (1 W ) W o Solving for W nd W gives : W o W o hpter 9-15

16 Exmples: For points A, B, nd D, specify the phse(s) present, the composition (in terms of wt% Ni) of ech phse, nd the reltive weight frction of ech phse o = 35 wt% Ni Phse Digrm: lss exmple At T A : Only iquid () =35 wt% Ni W = 100 wt%, W = 0 At T D : Only Solid ( ) α =35 wt% Ni W = 0, W = 100 wt% At T B : Both nd =32 wt% Ni α =43 wt% Ni W 73wt % W S R + S R R + S = 27 wt% T( ) T A 1300 T B 1200 T D 20 (liquid) u-ni system A B R S D 3235 o tie line (solid) Adpted from Fig. 9.3(b), llister 7e. (Fig. 9.3(b) is dpted from Phse Digrms of Binry Nickel Alloys, P. Nsh (Ed.), ASM Interntionl, Mterils Prk, OH, 1991.) hpter 9-16 wt% Ni

17 Summry Phse digrms re useful tools to determine: --the number nd types of phses, --nd the composition of ech phse --the weight frction reltive mount of ech of the phses for given T, P (often fixed) nd composition of the system under equilibrium condition hpter 9-17