36

Phn II Hp kim v bin i t chc

Chng 3 Hp kim v gin pha 3.1.3.1.3.1.3.1. Cu trc tinh th ca hp kimCu trc tinh th ca hp kimCu trc tinh th ca hp kimCu trc tinh th ca hp kim 3.1.1.3.1.1.3.1.1.3.1.1. Khi ni m v hp kimKhi ni m v hp kimKhi ni m v hp kimKhi ni m v hp kim a.a.a.a. nh ngh a nh ngh a nh ngh a nh ngh a Hp kim l hn hp ca kim loi vi mt hoc nhi u kim loi hoc kim khc. La tng= hp kim Cu + Zn hp kim n gi n ch gm 2 nguy n t Gang: Fe+Mn+Si v C+P+S, nguy n t ch nh l Fe (kim lo i) hp kim phc t p. Nguy n t kim lo i ch nh (> 50%) c gi l n n hay nguy n t c s . b.b.b.b. u vi t ca hp kimu vi t ca hp kimu vi t ca hp kimu vi t ca hp kim so vi kim loi so vi kim loi so vi kim loi so vi kim loi Hp kim: b n, cng, t nh chng m i mn cao hn, t nh cng ngh tt hn: c, c t gt, nhi t luy n ho b n tt hn, r hn. Kim lo i nguy n ch t: d n nhi t, d n i n tt (d y d n, trang sc, i n cc Pt, Au) c.c.c.c. Mt s khi ni mMt s khi ni mMt s khi ni mMt s khi ni m Pha: cng c u trc, cng tr ng th i, cng ki u v thng s m ng, c c t nh ch t c - l - ha x c nh, ph n c ch nhau bi m t ph n chia pha. C u t l c c ph n c l p c khi lng khng i, chng t o n n c c pha trong hp kim. H l t p hp c c pha, c th c n b ng ho c khng c n b ng. T o th nh hn hp c hc A + B KKKKhihihihi c tng tc: c tng tc: c tng tc: c tng tc: 2 trng hp x y ra: - ha tan th nh dung d ch r n, t chc mt pha nh kim lo i nguy n ch t (h nh 3.2b) dung mi - ph n ng vi nhau th nh hp ch t ha hc, t o th nh ki u m ng mi kh c h n. 3.1.2.3.1.2.3.1.2.3.1.2. Dung d ch rnDung d ch rnDung d ch rnDung d ch rn a. Khi ni m a. Khi ni m a. Khi ni m a. Khi ni m ---- phn loi phn loi phn loi phn loi /n:/n:/n:/n: l hp kim trong 1 hay nhi u nguy n t ho tan v o m ng tinh th ca kim lo i chi m a s c gi l n n. Dung mi chi m a s, nguy n t chi m t l t hn l ch t tan. /i m:/i m:/i m:/i m: ki u m ng ca dung mi, nng ch t tan c th thay i trong mt ph m vi m khng l m m t i s ng nh t . Dung d ch r n l ca B trong A: A(B), m ng ca A.

Tr ng th i khng c n b ng (3) = khng n nh: thng g p: khi tic t nh (b n, cng) cao hn, xu hng(1&2) Tr ng th i gi n nh (2) mun sang (1) ph i th ng G n nh (1). d.d.d.d. Phn loi cc tng tcPhn loi cc tng tcPhn loi cc tng tcPhn loi cc tng tc Ch t o hp kim = n u ch y % x c nh ri l m ngui. T pha lng ng nh t khi l m ngui s c tng t c t o n n c c pha kh c nhau.

G

1

3

2

H nh 3.1. S c c v tr n nh (1), gi n nh (2)

v khng n nh (3)

37 Cc ki u:Cc ki u:Cc ki u:Cc ki u: thay th v xen k (h nh 3.3) H nh 3.3. S sp xp nguyn t ha tan thay th v xen k vo dung mi c mng lp phng tm mt, mt (100) b.b.b.b. Dung d ch rn thay thDung d ch rn thay thDung d ch rn thay thDung d ch rn thay th

/n:/n:/n:/n: nguy n t ch t tan thay th v tr nguy n t dung mi. /ki n:/ki n:/ki n:/ki n: sai kh c dnguy n t khng qu 15%. T nh ch t ho l tng t nhau. Phn loi:Phn loi:Phn loi:Phn loi: theo gii h n h/tan gm 2 lo i: dd r n ho tan c h n v dd r n ho tan v h n

theo s ph n b ng/t ch t tan, c 2 lo i: dd r n c tr/t v dd r n o c tr/t GGGGii hn ha tan l nng ch t tan ln nh t m v n b o tn c m ng tinh th . i u ki n ho ti u ki n ho ti u ki n ho ti u ki n ho tan v hn:an v hn:an v hn:an v hn: ch c th (c khi o) x y ra khi tha m n c 4 y u t sau:

H nh 3.4. S thay th to dung dch rn ha tan v hn gia hai kim loi A v B 1- cng ki u m ng, 2-ng k nh nguy n t kh c nhau t (< 8%) 3-tho m n gii h n nng i n t: v d: m ng lftm Ce 1,36, lftk Ce 1,48, 4-c cng ho tr , t nh m i n sai kh c nhau t. Ngo i ra, t nh l - ha ( c bi t l nhi t ch y) ging nhau d t o th nh dung d ch r n ha tan v h n. V d: Ag - Au (m ng A1, r = 0,20%, cng nhm IB), Cu - Ni (m ng A1, r = 2,70%, IB v VIII), Fe - Cr (m ng A2, r = 0,70%, VIB v VIII). DDDDung d ch rn ung d ch rn ung d ch rn ung d ch rn cccc trt t trt t trt t trt t:::: c c nguy n t ch t tan s p x p c tr t t trong m ng tinh th dung mi, (c ngui r t ch m trong kho ng nO nh t nh). a s trng hp l khng tr t t. c.c.c.c. Dung d ch rn xen kDung d ch rn xen kDung d ch rn xen kDung d ch rn xen k /n:/n:/n:/n: c c nguy n t ha tan n m xen k v o c c l hng trong m ng tinh th dung mi. i u ki n:i u ki n:i u ki n:i u ki n: b n k nh nguy n t ch t tan ph i r t nh: N (0,071nm), C (0,077nm) v i khi c B (0,091nm) mi c kh n ng xen k v o c c l hng gia c c nguy n t ln nh Fe (0,1241nm), Cr (0,1249nm), W (0,1371nm), Mo (0,136nm),... L hng ln nh t trong m ng A1 l lo i 8 m t ch b ng 0,414dng/t , ngo i H, o c kim n o b lt y c c nguy n t ch bao quanh gi n ra, g y ra x l ch m nh m ng (h nh 3.5). . ch c dung d ch r n xen ha tan c h n. H nh 3.5. S x lch mng trong dd rn: a. ha tan thay th khi rht > rch, b. ha tan xen k rht> rl hng d.d.d.d. Cc c t nh ca dung d ch rnCc c t nh ca dung d ch rnCc c t nh ca dung d ch rnCc c t nh ca dung d ch rn C ki u m ng tinh th ca kim lo i dung mi c c trng c, l , ha t nh ca kim lo i n n: 1) M ng tinh th , n gi n v x t ch t (A1, A2...) ca kim lo i vi li n k t kim lo i 2) C t nh ging kim lo i c s:

thay

th

xen k

a-th

ay th

b-xen k

ban

u

38 . d o, c gi m i 1 cht song v n cao, d bi n d ng d o, c bi t t ng d o: Cu(Zn) vi 30%Zn cn d o hn c Cu chi ti t d p s u, d t = latng . t ng b n, cng, kh n ng ch u t i hn h n kim lo i nguy n ch t . nng ch t tan c ng ln d o c ng gi m, b n c ng t ng. Qu ln g y ra gin, d b g y, v chn nng th ch hp. 3) D n nhi t, d n i n tt nhng k m hn kim lo i nguy n ch t, thay i t nh chng n mn. Dung d ch r n l pha c b n chi m ti 90% th m ch 100% trong v t li u k t c u. 3.1.3.3.1.3.3.1.3.3.1.3. Pha trung gianPha trung gianPha trung gianPha trung gian Tr n gi n pha 2 ph a l dung d ch r n, gia l c c pha trung gian. a.a.a.a. Bn cht v phn loiBn cht v phn loiBn cht v phn loiBn cht v phn loi c i m: 1) C m ng tinh th phc t p v kh c h n vi nguy n t th nh ph n

2) C t l ch nh x c gia c c nguy n t theo cng thc ha hc AmBn 3) T nh ch t : kh c h n c c nguy n t th nh ph n gin 4) C nhi t ch y x c nh, khi t o th nh ta nhi t.

5) kh c vi c c hp ch t ha hc thng thng, c c pha trung gian khng ho n to n tu n theo quy lu t ha tr khng c th nh ph n ha hc ch nh x c theo cng thc, c li n k t kim lo i. C c pha trung gian trong hp kim thng g p: pha xen k , pha i n t v pha Laves. b.b.b.b. Pha Pha Pha Pha xen kxen kxen kxen k /n:/n:/n:/n: L pha t o n n gia c c kim lo i chuy n ti p (c b n k nh nguy n t ln) vi c c kim c b n k nh nguy n t b nh C, N, H (v B): cacbit, nitrit, hyrit (v borit). /i m:/i m:/i m:/i m: M ng tinh th ca pha xen k tng quan k ch thc nguy n t gia kim (X) v kim lo i (M):. khi rX / rM < 0,59 mt trong ba ki u m ng l A1, A2, A3 (tuy khng gi l i ki u m ng vn c nhng v n mang c i m kim lo i), c c nguy n t kim xen k v o c c l hng trong m ng, t o n n hp ch t vi c c cng thc n gi n nh M4X, M2X. . khi rX / rM > 0,59 m ng tinh th phc t p (c gi l pha xen k vi m ng phc t p) tng ng vi cng thc M3X, M7X3, M23X6. TTTT/cht:/cht:/cht:/cht: Nhi t ch y r t cao (thng > 2000 3000oC), r t cng (HV > 2000 5000) v gin ha b n, n ng cao t nh chng m i mn v ch u nhi t ca hp kim. H v N c k ch thc nguy n t nh n n rX / rM < 0,59, Fe4N, Fe2N, Mo2N, Cr2N... c m ng n gi n. C c rX / rM>0,57 n n t o Fe3C, Mn3C, Cr7C3, Cr23C6,WC, TiC, Mo2C, VC m ng phc t p t ng cng v t nh chng m i mn ca hp kim. c.c.c.c. Pha i n t Pha i n t Pha i n t Pha i n t (Hum - Rothery) /n:/n:/n:/n: L pha c ki u m ng x c nh, t o th nh vi nng i n t N x c nh (s i n t ha tr /s nguy n t): 3/2 (21/14), 21/13 v 7/4 (21/12), mi t l ng vi mt c u trc m ng phc t p nh t nh. Thng l hp kim ca Cu, Ag, Au vi Zn, Sn, Cd. Vi Cu1+, Zn2+ ta c:

Ce = 21/14 pha m ng A1: CuZn, AgZn, AuZn (Ce=(1.1+1.2)/2=3/2) Ce = 21/13 pha m ng lf phc t p: Cu5Zn8, Ag5Sn8 (Ce=(5.1+8.2)13=21/13) Ce = 21/12 pha , m ng lgxc: CuZn3, AgZn3 (Ce=(1.1+3.2)/4=7/4=21/12) d.d.d.d. Pha LavesPha LavesPha LavesPha Laves /n:/n:/n:/n: Pha t o bi hai nguy n t A, B c t l b n k nh nguy n t rA / rB = 1,2 (1,1 1,6) vi cng thc AB2 c ki u m ng A3: MgZn2, MgNi2 hay A1 (MgCu2). Do gin n n ch c dng trong HKTG ho c c c pha ho b n.

39 3.2.3.2.3.2.3.2. Gin pha ca h hai cu tGin pha ca h hai cu tGin pha ca h hai cu tGin pha ca h hai cu t /n:/n:/n:/n: GP l gi n bi u th s bi n i th nh ph n v tr ng th i pha c n b ng theo nhi t v th nh ph n ca h di p su t khng i (1 at). Cch bi u di n:Cch bi u di n:Cch bi u di n:Cch bi u di n: c i m: GP ch ng v ph hp vi hp kim tr ng th i c n b ng (ngui r t ch m hay ), Cng dng:Cng dng:Cng dng:Cng dng: x c nh c u trc ca hp kim, x c nh no ch y, chuy n bi n pha n u luy n v x l nhi t, gia cng (bi n d ng, c, r n, c n, k o,..), r t quan trng. 3.2.1.3.2.1.3.2.1.3.2.1. Quy tc pha v ng dngQuy tc pha v ng dngQuy tc pha v ng dngQuy tc pha v ng dng Quy t c pha ca Gibbs: T= N-F+2 khi P=1at th T=N-F+1 TTTT====0 0 0 0 h b t bi n, c % v no, lc F = N + 1 (s pha=s c u t +1). V d kim lo i nguy n ch t (N = 1) khi nng ch y: T=1-2+1=0 nhi t khng i. T=1:T=1:T=1:T=1: V d, khi k t tinh HK 2 nguy n: (T = 2 - 2 + 1=1) k t tinh ho c nng ch y trong kho ng nhi t ho c %. TTTT = 2 = 2 = 2 = 2:::: h cng mt lc c th thay i c hai y u t nhi t v th nh ph n c i m: c i m: c i m: c i m: T 0 s pha nhi u nh t ca h ( tr ng th i c n b ng!) Fmax = N + 1 h mt c u t Fmax = 2, hai c u t Fmax = 3, ba c u t Fmax = 4. 3.2.2. Quy tc n by3.2.2. Quy tc n by3.2.2. Quy tc n by3.2.2. Quy tc n by /n:/n:/n:/n: l quy t c cho ph p x c nh t l ca c c pha, c c t chc tr n GP. Bi u thc: Bi u thc: Bi u thc: Bi u thc:

QA.XA=QB.XA Trong vng 2 pha: i m kh o s t c ng g n pha n o th t l pha y c ng ln

+=

+=

XXX%

XXX

%

FA.XA=FB.XB FA=FB(XB/XA)

M.X=M.X 3.2.3.3.2.3.3.2.3.3.2.3. Gin lGin lGin lGin loi Ioi Ioi Ioi I /n: /n: /n: /n: L GP ca h 2 c u t khng c b t k tng t c n o vi nhau. M t:M t:M t:M t: AEB l ng lng, CED (245oC) l ng r n, l nhi t ch y (k t tinh): B, A (h nh 3.9a), i n h nh l h Pb - Sb h nh 3.9b. (Pb ch y 327oC), (Sb ch y- 631oC). kho ng gia hai ng lng v ng c: kho ng k t tinh. a) b)

H nh 3.9. Dng tng qut ca gin pha loi I (a) v gin pha Pb - Sb (b).

Hp kim 1: 60%Sb + 40%Pb. B t u ng c 1 (500oC), k t thc ng c 2 (245oC)

FA FB XA XB

T

%B

M

X X

L

L+B A+L

B+(A+B)

E A

B

A+B

A+ (A+B)

100%A 100%B %B

nhi

t L

L+Sb Pb+L

E 327

631

[Pb+

Sb]

Pb Sb %Sb

nhi

t

13

a a a

1 1

60

245

Sb+[Pb+Sb]

37

b bb

40

+ > 500oC lng ho n to n L, < 245oC r n ho n to n, trong kho ng (500 245oC) 2 pha (lng + r n) = (L + Sb). Khi l m ngui th tinh th B (Sb) t o th nh c ng nhi u. p dng quy tc cnh tay np dng quy tc cnh tay np dng quy tc cnh tay np dng quy tc cnh tay n:::: - t i i m a t l pha r n %Sb= aa/aa=(60-37)/(100-37)= 36,5%, pha lng %L=63,5% - t i i m b t l pha r n %Sb= bb/bb= (60-13)/(100-13)=54%, pha lng %L=46% p dng quy tc pha:p dng quy tc pha:p dng quy tc pha:p dng quy tc pha: t i i m 1& a T=2-2+1= 1 ng c trong kho ng noc th thay i tr n i m 1 T=2-1+1=2 thay i c % v no m pha lng (h ) v n b o tn t i i m cng tinh E T=2-3+1=0 ng c cng tinh th no khng i ging KL ng/ch t Ph n ng cng tinh: LE (A + B) hay L13%Sb (Pb + Sb). Hp kim c th nh ph n ch nh i m E hp kim cng tinh, c nhi t ch y th p nh t, Hp kim < 13%Sb = HK trc cng tinh, HK>13%Sb sau cng tinh (t kh o s t HKTCT) 3.2.4.3.2.4.3.2.4.3.2.4. Gin loi IIGin loi IIGin loi IIGin loi II /n: l GP ca h 2 c u t ho tan v h n tr ng th i r n v lng (h nh 3.10) H i n h nh Cu - Ni h nh 3.10.a v h Al2O3 - Cr2O3 h nh 3.10b. S biu din s hnh thnh t chc khi kt tinh cc nhit khc nhau. a) b)

H nh 3.10. Gin pha loi II, h Cu-Ni (a) v h Al2O3 - Cr2O3 (b). 3.2.5.3.2.5.3.2.5.3.2.5. Gin loi IIIGin loi IIIGin loi IIIGin loi III /n:/n:/n:/n: L gi n pha ca h hai c u t , ha tan c h n tr ng th i r n v c t o th nh cng tinh, h nh 3.12. H i n h nh l Pb-Sn. D ng kh ging vi gi n lo i I, kh c nhau y l + Tng t nh gi n lo i I, nhi t ch y ca HK gi m khi t ng c u t th hai.

c c dung d ch r n c h n v thay th cho c c c u t A v B. AEB - ng lng, ACEDB- ng r n. H nh 3.12. Gin loi III, h Pb - Sn v s hnh thnh t chc khi kt tinh trng thi cn bng ca hp kim

F

G

A

B 245

200

19,2 61,9 97,5 183

100

13,3

300

20 40 60 80 Sn Pb %Sn

E a a

2

3

4

1

2

C D

+Sn

18,5 57

nhi

t

, oC

L L+40%S1

13,3%Sn L40%Sn 2

3 4

%Cr2O3 Cr2O3 Al2O3 20 40 80 60

2000

2100

2200 nh

it

,

L

L+

2266

2045

%Ni Ni Cu 20 40 80 60

1000

1200

1400

nhi

t

1455

1083

ng

ng

L

L+

1

2 2

0

1

41 + i m cng tinh E vi ph n ng cng tinh : LE [+] hay L61,9 [19,2+ 97,5] + HK < 61,9%Sn trc cng tinh (tr i E) v HK> 61,9%Sn HK sau cng tinh (ph i E) + CF v DG l gii h n ha tan. ha tan max nhi t cng tinh 183oC + C th chia c c hp kim ca h th nh ba nhm sau. Nhm cha r t t c u t th hai (b n tr i F, b n ph i G), sau khi k t tinh xong ch c mt dung d ch r n ho c , c c t nh nh gi n lo i II. Nhm c th nh ph n n m trong kho ng (t F n C v D n G), no< CF v DG II&II. Nhm gi u nguy n t HK (t C n D), sau khi ti t ra dung d ch r n (C hay D), pha lng cn l i i m cng tinh E. Kh o s t HK 40%Sn ca h Pb - Sn (h nh 3.12). - Tr n 245oC HK ch y lng ho n to n, 245oC hp kim b t u k t tinh ra 2 vi 13,3%Sn, ngui ti p tc dung d ch r n AC, pha lng cn l i AE chi u t ng l n ca h m lng Sn. p dng quy t c n b y: 200oC pha cha 18,5%Sn (a) v L cha 57%Sn (a), %r n= (57-40)/(57-18,5) = 44,2%, %L = 55,8% nhi t cng tinh (LE [C + D]), %L=(61,9-40)/(61,9-19,2)=51,3%, v %=48,7% trong cng tinh %=(97,5-61,9)/(97,5-19,2)= 45,5% v %=54,5%

/i m: /i m: /i m: /i m: hai lo i dung d ch r n : lo i k t tinh u ti n tr n 183oC v lo i cng k t tinh vi nhi t khng i (183oC) v c gi l cng tinh (b qua II). H nh 3.13 l t chc t vi ca hai hp kim h n y. 3.2.6.3.2.6.3.2.6.3.2.6. Gin loi IVGin loi IVGin loi IVGin loi IV /n: L GP hai c u t c t o th nh hp ch t ha hc AmBn,

Tr n y l bn gi n pha hai c u t c b n nh t, thc t cn c nhi u ki u gi n pha phc t p vi c c ph n ng kh c.

3.2.7.3.2.7.3.2.7.3.2.7. Cc ginCc ginCc ginCc gin pha vi cc phn ng khc pha vi cc phn ng khc pha vi cc phn ng khc pha vi cc phn ng khc GGGGP vi cc pP vi cc pP vi cc pP vi cc phn ng bao tinh (peritectic) (peritectic) (peritectic) (peritectic)::::L+R1R2.V d GP Fe-CL0,5+ 0,1 0,16

D ng i n h nh l h HK Mg-Ca (h nh 3.14) vi hp ch t ho hc n nh Mg4Ca3, = tng ca hai gi n lo i I: Mg - Mg4Ca3 v Mg4Ca3-Ca. c kh o s t nh 2 gi n c l p.

H nh 3.14. Gin loi IV, h Mg-Ca %Ca

Ca Mg 20 40 80 60

400

600

800

nhi

t

,

55,3

L

L+Ca

Mg4Ca3+Ca Mg+Mg4Ca3

L+Mg4Ca3

Mg4Ca3+L Mg+L

516 445

H nh 3.13. T chc t vi ca hp kim Pb - Sb: a. cng tinh [+], mu ti l giu Pb, b. trc cng tinh vi 40%Sn [ c lp l cc ht ln mu en b bao bc bi cng tinh [+]

42 /i m:/i m:/i m:/i m: r n mi R2 n m gia Lbt& R1 tr n GP, p/ bao tinh khng x y ra ho n to n, v R2 t o th nh bao bc l y R1 t o n n lp m ng ng n c ch khng cho ph n ng ti p tc. GP c phn ng cng t ch (eutectoid) (eutectoid) (eutectoid) (eutectoid):::: R [R1+R2] /i m:/i m:/i m:/i m: kh c vi ph n ng cng tinh, cng t ch l pha r n 2 pha r n. V d: GP Fe - C: Fe(C)0,8 [Fe + Fe3C] (s kh o s t sau). S ti t pha khi dung d ch r n Ti t pha II & II (h nh 3.12) l c c ph n t nh m n, ph n t n, ph n b u trong n n pha m ho b n ha b n ti t pha.

3.2.8.3.2.8.3.2.8.3.2.8. Quan h gia dng gin pha v t nh cht ca hp kimQuan h gia dng gin pha v t nh cht ca hp kimQuan h gia dng gin pha v t nh cht ca hp kimQuan h gia dng gin pha v t nh cht ca hp kim a. a. a. a. T nh cht cc pha thnh phnT nh cht cc pha thnh phnT nh cht cc pha thnh phnT nh cht cc pha thnh phn Hp kim c t chc mt pha t nh ch t ca hp kim l t nh ch t ca pha HK c t chc bao gm hn hp ca nhi u pha th t nh ch t ca hp kim l s tng hp hay k t hp t nh ch t ca c c pha th nh ph n (khng ph i l cng n thu n), gm c c trng hp: HK l DDR (dung d ch r n) + c c pha trung gian: Quan h t nh ch t - nng thng thng c x c nh b ng thc nghi m. /i m t nh cht v s h nh thnh:/i m t nh cht v s h nh thnh:/i m t nh cht v s h nh thnh:/i m t nh cht v s h nh thnh: DDDDung d ch rnung d ch rnung d ch rnung d ch rn (t nh ch t g n ging vi KL dung mi), thng r t d o, dai v m m, Pha trung gian Pha trung gian Pha trung gian Pha trung gian : : : : t nh ch t kh c h n vi c c c u t nguy n ch t: cng ho c r t cng, gin. PPPPha trung gian ch xut hi n ha trung gian ch xut hi n ha trung gian ch xut hi n ha trung gian ch xut hi n khi a c u t th hai v o vi lng vt qu gii h n ha tan. b.b.b.b. T nh cht ca hn hp cc phaT nh cht ca hn hp cc phaT nh cht ca hn hp cc phaT nh cht ca hn hp cc pha: Quan h tuy n t nh:: Quan h tuy n t nh:: Quan h tuy n t nh:: Quan h tuy n t nh: h nh 3.16, n gi n nh t T nh ch t ca hn hp : = 1

niiXTT , trong Ti v Xi l t nh ch t v t l ca pha i, i

vi hp kim 2 pha: PHK = T1X1 + T2.X2 hay PHK = T1 + X2.(T2 - T1). Vi Xi GP (h nh 3.16)

H nh 3.16. T nh cht ca hp kim v gin pha - quan h tuyn t nh q/h tuy n t nh ch ng khi cng c h t v c c pha ph n b u n.

%B B A

nhi

t

, P

L L+B A+L

P

A+B

%B AmBn A

nhi

t

, P

L +L

P

L+AmBn

+AmBn

%B B A

nhi

t

, P

L

L+

P PA

PB

%B B A

nhi

t

, P

L +L

P

L+

+

P

P PA PB

P PAmBn

43 Quan h phi tuy n:Quan h phi tuy n:Quan h phi tuy n:Quan h phi tuy n:. Trong trng hp h t nh i ho c to l n, t nh ch t t c s thay i tu theo trng hp: h t nh di dai t ng = b n + d o t ng Ch nh v th m t nh ch t ca hp kim c th khng cn tu n theo quan h tuy n t nh nh t l t i i m cng tinh, cng t ch v l n c n (h nh 3.17). H nh 3.17. Quan h phi tuy n gia t nh ch t v GP

3.3.3.3.3.3.3.3. Gin pha Fe Gin pha Fe Gin pha Fe Gin pha Fe ---- C (Fe C (Fe C (Fe C (Fe ---- Fe Fe Fe Fe3333C)C)C)C) Gi n pha Fe - C (ch x t h Fe - Fe3C) kh phc t p, r t i n h nh minh ha c c tng t c thng g p v c s dng r t nhi u trong thc t . Ngo i ra cn c gi n Fe - grafit l h c n b ng n ch y u l dng trong gang. 3.3.1.3.3.1.3.3.1.3.3.1. Tng tc gia Fe v CTng tc gia Fe v CTng tc gia Fe v CTng tc gia Fe v C Fe,Fe,Fe,Fe, kh d o (d bi n d ng ngui), dai, tuy b n, cng hn Al, Cu nhi u song v n cn r t th p so vi y u c u s dng. Khi a C v o Fe gia ha b n, r hn HK Fe-C tr n n thng dng a.a.a.a. S ha tan ca S ha tan ca S ha tan ca S ha tan ca CCCC vo vo vo vo FeFeFeFe To dung d ch rn xen k :To dung d ch rn xen k :To dung d ch rn xen k :To dung d ch rn xen k : b n k nh nguy n t rC = 0,077nm, rFe = 0,1241nm) C ch c th ha tan c h n v o Fe d ng dung d ch r n xen k . Fe c 2 ki u m ng tinh th : lftk A2 (no < 911oC - Fe v 1392 1539oC - Fe) v lftm A1 (911 1392oC - Fe), kh n ng ha tan cacbon v o c c pha Fe kh c nhau: FeFeFeFe v Fe v Fe v Fe v Fe vi m vi m vi m vi mng ng ng ng A2A2A2A2 tuy m t x p th p, c nhi u l hng, song mi l hng l i c k ch thc qu nh (l t m m t c r = 0,02, l bn m t ln hn c r = 0,036), ln nh t cng ch b ng 50% k ch thc ca nguy n t s t Fe ch ho tan c 0,02%C v Fe 0,1%C. FeFeFeFe v v v v Fe Fe Fe Fe, Fe, Fe, Fe, Fe vi mng A1 vi mng A1 vi mng A1 vi mng A1:::: tuy c m t x p cao hn, nhng l hng l i c k ch thc ln hn (l bn m t r = 0,028nm, l t m m t r = 0,051nm), v n cn hi nh nhng nh c c nguy n t s t c th gi n ra Fe ha tan c cacbon 2,14%C. b.b.b.b. Tng tc ha hc Tng tc ha hc Tng tc ha hc Tng tc ha hc gia Fe v Cgia Fe v Cgia Fe v Cgia Fe v C Austenit () l DDR ca C trong Fe, m ng A1, g/h n ho tan: 727oC -0,8%C, 1147oC-2,14%C Ferit () l DDR ca C trong Fe, m ng A2, gii h n ho tan: 20oC-0,006%C, 727oC-0,8%C Fe3C l pha xen k , c ki u m ng phc t p, c th nh ph n 6,67%C + 93,33%Fe. 3.3.2.3.3.2.3.3.2.3.3.2. Gin pha Fe Gin pha Fe Gin pha Fe Gin pha Fe ---- Fe Fe Fe Fe3333C v cc t chcC v cc t chcC v cc t chcC v cc t chc a.a.a.a. Gin pha Fe Gin pha Fe Gin pha Fe Gin pha Fe ---- Fe Fe Fe Fe3333C C C C H nh 3.18 vi c c k hi u c c ta (no, oC - %C) nh sau: Mt s ng c ngh a thc t rt quan trng:Mt s ng c ngh a thc t rt quan trng:Mt s ng c ngh a thc t rt quan trng:Mt s ng c ngh a thc t rt quan trng: - ABCD l ng lng x c nh nhi t ch y c - AHJECF l ng r n k t tinh ho n to n c. - PSK (727oC) l ng cng t ch nhi t luy n - ES - gii h n ha tan cacbon trong Fe ho nhi t luy n, nhi t luy n.

%B B A

nhi

t

, P

L +L

P

L+

+ P

P

44

- PQ - gii h n ha tan cacbon trong Fe nhi t luy n k m quan trong hn A (1539 - 0) B (1499 - 0,5) C (1147 - 4,3) H (1499 - 0,10) P (727 - 0,02) Q (0 - 0,006) S (727 - 0,80) D (~1250 - 6,67) E (1147 - 2,14) K (727 - 6,67) G (911 - 0) F (1147 - 6,67) J (1499 - 0,16) N (1392 - 0) H nh 3.18. Gin pha Fe - C (Fe - Fe3C) b. Cc chuy n bi n khi lm ngui chmb. Cc chuy n bi n khi lm ngui chmb. Cc chuy n bi n khi lm ngui chmb. Cc chuy n bi n khi lm ngui chm - Chuy n bi n bao tinh x y ra 1499oC: H + LB J hay 0,10+ L0,50 0,16 (3.1) - Chuy n bi n cng tinh x y ra 1147oC: LC (E + X ) hay L4,3 (2,14+ X ) (3.2) - Chuy n bi n cng t ch x y ra 727oC: S [P + X ] hay 0,8 [0,02+ X ] (3.3) - S ti t pha Fe3C d ra khi dung d ch r n ca cacbon: , no< ES X II v , no< PQ X III. c.c.c.c. Cc t chc mt phaCc t chc mt phaCc t chc mt phaCc t chc mt pha FeritFeritFeritFerit (, F, F, F, F), n u tr n, Ferit l pha tn t i nhi t thng, t l cao nh t (ti 90%), quan trng i vi c t nh ca hp kim Fe - C. T chc t vi ca ferit (xem h nh 3.22) c d ng c c h t s ng, a c nh. Austenit Austenit Austenit Austenit [, AAAA, FeFeFeFe(C)(C)(C)(C)], n u tr n, kh c vi F, khng c t nh s t t , ch tn t i nhi t cao (> 727oC), ch tn t i nhi t cao ho c TKG austenit, 13, nhng l i c vai tr quy t nh trong bi n d ng nng v nhi t luy n. T nh ch t ca : : : : c t nh d o r t cao (m ng A1). Nh c t nh d o cao c t nh d o cao c t nh d o cao c t nh d o cao th ti n h nh bi n d ng nng mi hp kim Fe - C vi C < 2,14% L m ngui austenit vi tc t chc c t nh : ngui ch m P+F m m, ngui nhanh mactenxit cng. T chc t vi ca gm c c h t s ng, c th vi m u m nh t kh c nhau i cht, c c c ng song tinh. X mX mX mX mentitentitentitentit (XXXX , FeFeFeFe3333CCCC): l pha xen k vi ki u m ng phc t p c cng thc Fe3C v th nh ph n 6,67%C, cng v gin, cng vi ferit n t o n n c c t chc kh c nhau ca hp kim Fe - C. Ngi ta ph n bi t 4 lo i X : - XeI ti t ra t pha lng khi l m ngui HK > 4,3%C. X I c d ng th ng, th to (h nh 3.24b) i khi c th th y c b ng m t thng.

+L

L

E C

P

G

J

B A H

Q

F+P pe

clit

l

bu

ri

P+X I P+X II+L L + X I

727

1147

A3

Acm

L+X

Fe Fe3C 0,8 2,14 4,3

910

1200

nhi

t

, o C

%C

1 2 3 4 5 6

500

D

F

K +X II +X II+L L + X I S

45

- XeII c t o th nh l m ngui theo ng ES HK c 0,80

46 GangGangGangGang:::: tng ng vi GP Fe-C (Fe-Fe3C) l gang tr ng, t dng v qu cng, gin, khng th gia cng c t c gm 3 lo i: - Gang trng trc cng tinh vi %C< 4,3%, c t chc P+ X II + L (h nh 3.24a). - Gang trng cng tinh c 4,3%C, ng i m C hay l n c n, vi t chc ch l L (h nh 3.21). - Gang trng sau cng tinh vi > 4,3%C b n ph i i m C, c t chc L + X I (h nh 3.24b). H nh 3.23. T chc t vi ca thp sau cng t ch H nh 3.24. T chc t vi ca gang trng (x500): (1,20%C) (x500). trc cng tinh (a) v sau cng tinh (b) c.c.c.c. Cc i m ti hn ca th pCc i m ti hn ca th pCc i m ti hn ca th pCc i m ti hn ca th p A (t ti ng Ph p arr t=dng, c- chauffer=nung nng, r- refroidir=l m ngui) A vi 1, 2, 3, 4, v cm, chng c gi l c c i m (hay nhi t ) ti h n, gm: A1 - ng PSK (727oC) ng vi chuy n bi n austenit peclit, c trong mi lo i th p. A3 - ng GS (911 727oC) ng vi b t u ti t ra F khi khi l m ngui hay k t thc ha tan ferit v o austenit khi nung nng, ch c trong th p trc cng t ch. AAAAcm cm cm cm ---- ng ES (1147 727oC) ng vi b t u ti t ra X II khi khi l m ngui hay k t thc ha tan X II v o khi nung nng, ch c trong th p sau cng t ch. AAAA0000---- (210oC) - i m Curi ca X , A2- (768

oC) - i m Curi ca ferit, Cng mt th p bao gi cng c: Ac1 > A1 > Ar1; Ac3 > A3 > Ar3...,

H nh 3.22. T chc t vi ca thp trc cng t ch (x500): a. 0,10%C, b. 0,40%C, c.0,60%C.

HOP KIM VA GIAN DO PHACau truc tinh theKhai niem ve hop kimDung dich ranPha trung gian

Gian do phaQuy tac phaQuy tac don bayGD pha loai IGD pha loai IIGD pha loai IIIGD pha loai IVCac phan ungQuan he giua GDP va tinh chat

GDP Fe-CTuong tac giua Fe va CGDP Fe-C va to chucPhan loai Thep - Gang

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