chuong 3 gian do pha.pdf

7/25/2019 Chuong 3 Gian Do Pha.pdf

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Chng 3: HP KIM & GIN PHA


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3.1. Cu trc tinh th ca hp kim

Hn hp ca kim loi vi cc kim loihoc kim khc; nguyn t chnh - nn.

u im: bn, cng, tnh chng

mi mn cao hn, tnh cng ngh tt hn,nhit luyn ho bn tt hn, r hn.

3.1.1. Khi nim v hp kim

Vt liuGii hn bn

ko , MPaGii hn

chy, MPa dndi, %

cng,HB

Al 99,95% 50 10 45 15AA7075 228 103 17 60

AA7075(ti+ha gi)

600 560 11 150

AA7075: 6%Zn, 2,4%Mg, 1,6%Cu, Mn0,3%


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Pha APha B


3.1. Cu trc tinh th ca hp kim

3.1.1. Khi nim v hp kimMt s khi nim:

Pha: phn ng nht ca h ccng cu trc, trng thi, kiumng, c tnh cht c-l-ho tnhxc nh, phn cch nhau bi bmt phn chia pha;

Cu t: l cc nguyn t (hochp cht ho hc bn vng) to

nn pha trong hp kim;

H: tp hp cc pha, c th trng thi cn bng, hoc khngcn bng.


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Phn loi tng tc trong hp kim

Khng c tng tc:

Cc kim loi ha tan ln nhau trng thi lng, khng ha tan trng thi rn, to hn hp c hc hai pha A + B.

C tng tc:- Ho tan vo nhau to dung dch rn A(B) - (gi nguyn kiumng ca nn A);- Phn ng to hp cht ha hc vi kiu mng mi khc hn.

A

B

A(B)

L (A+B)


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3.1.2. Dung dch rnKhi nim: l pha ng nht, c cu trc mng nh ca dung

mi (kim loi nn), cc nguyn t cht ha tan sp xp li trongmng dung mi mt cch u n v ngu nhin.

K hiu: A(B) = Dung dch rn ca B ha tan trong A.

Dng dch rn thay th: cc nguyn t cht tan thay th v tr

cc nguyn t dung mi trong mng tinh th (dnt sai khc


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Dung dch rn xen k: cc nguyn t ha tan nm xen kvo cc l hng trong mng tinh th dung mi.

bn knh nguyn t ha tan rt nh, gii hn ha tan thp.Cc c tnh ca dung dch rn: cc trng c, l, ha tnh ca kim loinn:

- Kiu mng tinh th n gian: A1,A2 vi lin kt kim loi;

- do c gim nhng vn cao;

-Tng cng, bn, tnh chngmi mn r rt so vi kim loi nguyn

cht;- Nng cht tan tng tng bn, gim do.

-Thay i tnh chng n mn, dn in, nhit km KL nguyn cht;

- L pha c bn chim hn 90% trong vt liu kt cu.


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Al

Fe

Ni

Al

Al3

Ni

AlFe3

Pha trung gian: cc hp cht ho hc c trong hp kim,nm gia hai vng dung dch rn trn gin pha.

c im:- C kiu mng tinh th phc tp,khc hn vi cc nguyn t thnhphn;

- C t l gia cc nguyn t cngthc xc nh AmBn;

- Tnh cht khc hn so vi ccnguyn t thnh phn (gin);

- C nhit nng chy xc nh,khi to thnh ta nhit.


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3.2 Gin pha ca h hai cu t

Quy tc pha: F = C P + 1

K/n : Gin biu din s bin i t chc pha ph thucvo nhit v thnh phn ca h trng thi cn bng.

= A(B) = B(A)

F - s bc t do, C - scu t, P - s pha.

Nhit,

C0

Thnh phn, % B100%

A100%

B

L

+L +L

+

25% B


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nh hng ca nhit v thnh phn

- T thay i - s lng pha thay i (ng AB);

- C% thay i - s lng pha thay i (ng BD).

% ng (C12H22O11)

Nhit , 0C

1 pha 2 pha

L + R


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X X

M M

3.2. Gin pha ca h hai cu t

Quy tc n by: M . X = M . X

Nhit,

C0

Thnh phn, % B

L

+L +L

+25% B

X X

C C

.100%C-CC-C

XXX

)XX

(MM

MMM

M% 0

C0


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Gin pha loi 1:

Gin pha ca h hai cu t khng c bt k tng tc no

vi nhau (Pb-Sb).aEb ng lng;

cEd ng c;

a, b nhit chy

caA v B;E im cng tinh:

L (A + B)

A B

Lng (L)

L+BA+L

Nhit

(A+B)

(A+B)+BA+(A+B)

a

E

b

c d

%B

t

C

DF

X

A B

(A+B)


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Gin pha loi 2

Gin ca h hai cu

t tng tc v ho tanv hn vo nhau

trng thi rn, v d:

(Cu-Ni, Al2O3-Cr2O3)

amb ng lng

anb ng c

A B

%B

Lng (L)

L+

Nh

it

a

bm

n

X

C

d c f

Cd Cf

?%;?%

?%;?%

B

ALL

= A(B) , B(A)


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Gin pha loi 3Gin ca h hai cu t tng tc v ho tan c hn vonhau trng thi rn (Pb-Sn, Cu-Ag).

A B

Lng (L)

L+

Nhit

+

a

E

b

c d

%B

L+

g f

X1 X2 X4

X3

aEb ng lng

acdb ng c

= A(B); = B(A)

E- im cng tinh:

L (+)


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Gin pha loi 4

Gin pha hai cu t c tng tc ho hc to ra pha trunggian A

mB

n(Mg-Ca Mg

4Ca

3) .

A B

Lng (L)

AmBn+B

Nhit

a

E1

b

E2L+A

AmBn

L+AmBn

L+AmBn

A+AmBnB+AmBn

c

Tch thnh hai gin pha 2 cu t n gin hn


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Quan h gia GP & tnh cht hp kimTnh cht ca hp kim l s tng hp hay kt hp tnh cht cacc pha thnh phn.


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rlt (max)= 0,036

3.3. Gin pha Fe-C (Fe-Fe3C)

Tng tc gia Fe v C

+ S ho tan ca C vo Fe: to cc dung dch rn xen k:

- Fe (A2; 13920

C): DDR = Fe(C), %Cmax = 0,1%, 14390

C+ Tng tc ho hc gia Fe v C Fe3C (%C = 6,67%)

rnt = 0,770 nm

C

rnt = 0,1241 nm

Fe

rlt (max)= 0,051 nm


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3.3. Gin pha Fe-C (Fe-Fe3C)

+XeII +XeII+Le(+Fe3C)

Le(+Fe

3C)

XeI+Le(+Fe3C)

L+XeI

XeI+Le(P+Fe3C)

P+XeII P+XeII+Le(P+Fe3C)+P

Fe Fe3C

L

+L

0,8

P[+Fe3

C]

15390C 14990C

13920C

9110C

ABH

N

J

CED

F

G

SP K

Q


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L

L

Cc chuyn bin khi ngui chm:Chuyn bin bao tinh: ti 14990C, im J:

0,1+ L0,5 0,16

Chuyn bin cng tinh: ti 11470C, im C:

L4,3 (2,14 + Fe3C)

Chuyn bin cng tch: ti 7270C, im S:

0,8 [0,02 + Fe3C]

P[+Fe3C]


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Cc t chc mt pha trn GP Fe-Fe3C

Ferit (, F ): Dung dch rn ho tan ca C

trong Fe ( gii hn ho tan 0,02%C ti7270C). T chc ht sng, a cnh.

Austenit (, A ): Dung dch rn ho tan ca Ctrong Fe ( gii hn ho tan 2,14%C ti 11470C,0,8%C ti 7270C). T chc ht sng + cc

ng song tinh.Xmentit (Fe3C, Xe ):

-XeI: sinh ra t Lng. Dng tm th, to.

-XeII: tit ra t austenit, dng li bao quanhht.

-XeIII: tit ra t ferit, thng khng b qua.

- Xe cng tch to thnh t c/b cng tch.


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Cc t chc hai pha trn GP Fe-Fe3C

Peclit (P ): hn hp cng tch ca F v Xe (88%F + 12%Xe)c to thnh t phn ng cng tch. Tn ti P tm v P ht.

Lburit (Le ): Hn hp cng tinh ca

A v Xe (>7270C), ca P v Xe (


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Phn loi thp-gang theo GP

K/n: Thp l hp kim ca Fe-C vi hm lng C < 2,14%,gang l hp kim ca Fe-C c 2,14%C.

c im:

- Nung nng thp trn GSE tt chc mt pha duy nht c do cao, d bin dng;

- Tnh c ca thp thp;

- Gang khng th nung nng t

trng thi mt pha nn gin,

cng, khng th gia cng bdng;

- So vi thp, gang c tnh c tt.

Thp Gang

P[

+Fe3C]


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Thp: theo GP c chia lm 3 loi:

- Thp trc cng tch (%C0,8%),t chc P + XeII ;

P[

+Fe3

C]

a b c


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Gang: tng ng vi GP lgang trng, gm 3 loi:

-Gang trng trc cng tinh(%C4,3), t chc XeI + Le.

d e f



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P[

+Fe3

C]

A3

Acm

A1

Cc im ti hn ca thpCc im (hay nhit ) ti hn -tng ng vi cc chuyn bin

pha trong thp, k hiu bng ch Avi ch s 1, 2, 3, 4 v cm.- A1 - ng PSK (727oC), ng vichuyn bin P [+Xe] , ctrong mi loi thp.

- A3 - ng GS (911 727o

C),ng vi chuyn bin + , chc trong thp trc cng tch.

- Acm - ng ES (1147 727oC)ng vi chuyn bin + X eII,

ch c trong thp sau cng tch.- Nung nng thm ch c, Lmngui thm ch r.

Ac1 > A1 > Ar1; Ac3 > A3 > Ar3; Accm > Acm > Arcm

A3 = 727 + 230(0,8-x) 0C; Acm = 727 + 313.(y 0,8) 0C; x,y : %C.


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