PY2N20 Material Properties and Phase Diagrams

Transcription

1 PY2N20 Mteril Properties nd Phse Digrms ecture 6 P. Stmenov, PhD School of Physics, TCD PY2N20-6

2 Microstructures in Eutectic Systems: I C o < 2 wt% Sn Result: - t extreme ends - polycrystl of grins i.e., only one solid phse. T( C) T E : C o wt% Sn : C o wt% Sn + (Pb-Sn System) b 0 C o (room T solubility limit) 30 C o, wt% Sn

3 Microstructures in Eutectic Systems: II 2 wt% Sn < C o < 18.3 wt% Sn Result: Initilly liquid + then lone finlly two phses polycrystl fine b-phse inclusions T( C) T E + + b : C o wt% Sn : C o wt% Sn b Pb-Sn system C o (sol. limit t T room ) 18.3 (sol. limit t T E ) 30 C o, wt% Sn

4 Microstructures in Eutectic Systems: III C o = C E Result: Eutectic microstructure (lmellr structure) - lternting lyers (lmelle) of nd b crystls. 300 Pb-Sn system 200 T E T( C) C : C o wt% Sn b b Microgrph of Pb-Sn eutectic microstructure 100 b b: 97.8 wt% Sn : 18.3 wt%sn 160 m Adpted from Fig. 9.14, Cllister 7e C E C, wt% Sn

5 mellr Eutectic Structure Other possible eutectic structures re: rod-like, globulr nd ciculr.

6 Microstructures in Eutectic Systems: IV 18.3 wt% Sn < C o < 61.9 wt% Sn Result: crystls nd n eutectic microstructure Just bove T E : T( C) 300 Pb-Sn system 200 T E R R + b : C o wt% Sn S S + b C o, wt% Sn b primry eutectic eutectic b C = 18.3 wt% Sn C = 61.9 wt% Sn S W = = 50 wt% R + S W = (1- W ) = 50 wt% Just below T E : C = 18.3 wt% Sn C b = 97.8 wt% Sn W S = = 73 wt% R + S W b = 27 wt%

7 Hypoeutectic & Hypereutectic 300 T( C) 200 T E b + b b (Pb-Sn System) C o, wt% Sn eutectic hypoeutectic: C o = 50 wt% Sn 61.9 hypereutectic: (illustrtion only) eutectic: C o = 61.9 wt% Sn b b b b b b 175 m 160 m eutectic micro-constituent

8 Intermetllic Compounds Mg 2 Pb Note: intermetllic compound forms line - not n re - becuse the stoichiometry (i.e. composition) is exct.

9 Eutectic Eutectic - liquid in equilibrium with two solids cool het + b

10 Exmple: Eutectoid & Peritectic Cu-Zn Phse digrm Peritectic trnsition + Eutectoid trnsition + Peritectoid solid stte Peritectic

11 Eutectoid & Peritectic Eutectoid - solid phse in equilibrium with two solid phses S 2 S 1 +S 3 intermetllic compound - cementite cool + Fe 3 C (727ºC) het Peritectic - liquid + solid 1 solid 2 S 1 + S 2 cool + (1493ºC) het περιτεκτικός περι - included

12 Iron-Crbon Phse Digrm Extrct Fe 3 C (cementite) 2 importnt points -Eutectic (A): + Fe 3 C -Eutectoid (B): + Fe 3 C α bcc (FM) β bcc (NM) obs. γ fcc (NM) δ bcc (NM) ε hcp (p >13 GP) T( C) + (ustenite) (Fe) R 0.76 C eutectoid B 1148 C R S A +Fe 3 C 727 C = T eutectoid +Fe 3 C +Fe 3 C S 4.30 C o, wt% C Fe 3 C (cementite-hrd) (ferrite-soft)

13 Perlite Fe 3 C (cementite-hrd) (ferrite-soft) 120 m Result: Perlite = lternting lyers of nd Fe 3 C phses

14 Hypoeutectoid Steel 0.76 Fe 3 C (cementite) w = s /( r + s ) w = (1- w ) T( C) + (ustenite) r s 727 C 1148 C + Fe 3 C + Fe 3 C +Fe 3 C (Fe-C System) w = S /( R + S ) w Fe3 C = (1- w ) (Fe) C 0 perlite w perlite = w C o, wt% C

15 Hypoeutectoid Steel perlite w perlite = w 100 m w = S /( R + S ) w Fe3 C = (1- w ) perlite Proeutectoid ferrite proeutectoid phse the first phse tht forms upon cooling the solid

16 0.76 Fe 3 C (cementite) Hypereutectoid Steel Fe 3 C w Fe3 C = r /( r + s ) w =(1- w Fe3 C ) w = S /( R + S ) w Fe3 C = (1- w ) T( C) C o + (ustenite) R perlite (Fe) w perlite = w r s S 1148 C +Fe 3 C +Fe 3 C (Fe-C System) +Fe 3 C C o, wt%c

17 Hypereutectoid Steel w = S /( R + S ) w Fe3 C = (1- w ) perlite w perlite = w 60 m perlite proeutectoid Fe 3 C

18 Exmple For 99.6 wt% Fe-0.40 wt% C t temperture just below the eutectoid, determine the following ) the mount of perlite nd proeutectoid ferrite () per 100 g of steel b) composition of Fe 3 C nd ferrite () c) the mount of crbide (cementite) in grms tht forms per 100 g of steel

19 Fe C (cementite) Solution. the mount of perlite nd proeutectoid ferrite () note: mount of perlite = mount of just bove T E C o = 0.40 wt% C C = wt% C C perlite = C = 0.76 wt% C C o C C C x g T( C) (ustenite) 1148 C + Fe 3 C +Fe 3 C perlite = 51.2 g proeutectoid = 48.8 g R S 727 C + Fe 3 C C C C o, wt% C C O

20 Fe C (cementite) Fe Solution - continued Fe3C Fe C 3 3 b) composition of Fe 3 C nd ferrite () c) the mount of crbide (cementite) in grms tht forms per 100 g of steel C 5.7 g 94.3 g C C o Fe 3 C C C x x g T( C) (ustenite) C O = 0.40 wt% C C = wt% C C Fe C = 6.70 wt% C C o, wt% C C R C O 727 C 1148 C + Fe 3 C S + Fe 3 C +Fe 3 C C Fe C 3

21 T Eutectoid ( C) C eutectoid (wt%c) Alloying Steel with More Elements T eutectoid chnges: C eutectoid chnges: Ti Mo Si W Ni Cr Ni Cr Mn Ti Si Mo W Mn wt. % of lloying elements wt. % of lloying elements

22 Txonomy of Metls Metl Alloys Ferrous Nonferrous Steels <1.4 wt% C Cst Irons wt% C Cu Al Mg Ti T( C) microstructure: ferrite, grphite cementite ustenite C Fe 3 C Eutectic: ferrite C Eutectoid: Fe 3 C +Fe 3 C Fe 3 C cementite (Fe) C o, wt% C

23 Steels incresing strength, cost, decresing ductility

24 Steel Types ( for your informtion only Not required for the exmintion!)