thermodynamic re-assessment of the mn-c system · iac mse nürnberg, sep. 1-4, 2008 content 1. aim...

IAC

Thermodynamic Re-assessment of

the Mn-C System

D. Djurovic and B. Hallstedt,

Materials Chemistry, RWTH Aachen University, Kopernikusstrasse 16, 52074

Aachen, Germany

J. von Appen and R. Dronskowski

Institute of Inorganic Chemistry, RWTH Aachen University, Landoltweg 1,

52056 Aachen, Germany

1

MSE Nürnberg, Sep. 1-4, 2008IAC

Content

1. Aim of investigations

2. Previous assessment

3. Thermodynamic modeling

4. Results

5. Conclusion

2


To provide a thermodynamic description of the Fe-Mn-C system which is as accurate and reliable as possible, especially at low temperatures.

Fe-Mn-C

Fe-C Mn-C Fe-Mn[Gus1985] [Wit2004][Hua1990]

P. Gustafson, Scand. J. Metall., 14 (1985) 259V. T. Witusiewicz et al., J. Phase Equilib., 25 (2004) 346

W. Huang, Scand. J. Metall., 19 (1990) 26

1. Aim of investigations

3


Fig. 1. Calculated phase diagram of the Mn-C system

An inverse miscibility gap above 4800 K

2. Previous assessment

Incorrect appearance of the Mn2C (hcp) phase

at low temperature

4


3. Thermodynamic modeling

CBCC (Mn)1(C,Va)1CUB (Mn)1(C,Va)1

FCC (Mn)1(C,Va)1HCP (Mn)1(C,Va)0.5BCC (Mn)1(C,Va)3

a. Solid Solution Phases

The carbon solution in manganese is described by

interstitial solution models with one sublattice occupied by

manganese atoms and the other one occupied by the both

carbon and vacancies.

5


b. Stoichiometric Phases

Mn23C6, Mn3C, Mn5C2 and Mn7C3

∆°G(MnnCm,T)=a+bT+∆cp(MnnCm,T)

∆cp(MnnCm,T)=0 (The Neumann-Kopp rule)

6


800 900 1000 1100 1200 1300 1400

-16000

-14000

-12000

-10000

-8000

-6000

-4000

-2000

0 [Moa1971]

[Tan1971]

[Ben1974]

[Ere1974]

[Du1988]

[Zai2004]

µ(M

n),

Jm

ol-1

Temperature, K

800 900 1000 1100 1200 1300 1400

-16000

-14000

-12000

-10000

-8000

-6000

-4000

-2000

0 [Moa1971]

[Tan1971]

[Ben1974]

[Ere1974]

[Du1988]

[Zai2004]

µ(M

n),

Jm

ol-1

Temperature, K

800 900 1000 1100 1200 1300 1400

-16000

-14000

-12000

-10000

-8000

-6000

-4000

-2000

0

[Ere1974]

[Du1988]

[Zai2004]

µ(M

n),

Jm

ol-1

Temperature, K

800 900 1000 1100 1200 1300 1400

-16000

-14000

-12000

-10000

-8000

-6000

-4000

-2000

0 [Moa1971]

[Tan1971]

[Ben1974]

[Ere1974]

[Du1988]

[Zai2004]

µ(M

n),

Jm

ol-1

Temperature, K

Fig. 2. Experimental data on the chemical potential of Mn in various phase

equilibria

Mn23C6/Mn

Mn23C6/Mn3C

Mn5C2/Mn3C

Mn23C6/Mn5C2

Mn5C2/Mn7C3

Mn7C3/Graphite

E Moattar et al., Trans. Farad. Soc., 67 (1971) 2303

H. Tanaka et al., Trans.Japan Inst. Metals, 35 (1971) 997

R. Benz, Metall. Trans., 5 (1974) 2217

V.N. Eremenko et al., Tugo plavkie Karbidy (Russ.), G.V. Samsonov, ed., "Naukova Dumka", Kiev, Ukr. SSR, 1970, 204

Du Sichen et al., Metall.Trans. B, 19 (1988) 951

A. I. Zaitsev et al., Dokl. Akad. Nauk SSSR, 395 (2004) 632

7


b. Stoichiometric Phases

Metastable end-members Mn2C (hcp) and MnC (fcc)

∆°G(MnnCm,T)=a+bT+∆cp(MnnCm,T)

∆cp(MnnCm,T)=0 (The Neumann-Kopp rule)

8


Calculated phase diagram of the Mn-C system

Hua1990

this work

4. Results

9


Calculated phase diagram of the Mn-C system

Hua1990

this work

10


200 400 600 800 1000 1200 1400 1600 1800

-18000

-16000

-14000

-12000

-10000

-8000

-6000

-4000

-2000

0

Mn3C

Liqud

Graphite

FCC

HCP

Mn5C

2

Mn7C

3

Mn23

C6

CBCC

µ(M

n),

Jm

ol-1

Temperature, K

200 400 600 800 1000 1200 1400 1600 1800

-18000

-16000

-14000

-12000

-10000

-8000

-6000

-4000

-2000

0

µ(M

n),

Jm

ol-1

Temperature, K

200 400 600 800 1000 1200 1400 1600 1800

-18000

-16000

-14000

-12000

-10000

-8000

-6000

-4000

-2000

0

Mn3C

Graphite

CBCC

Liquid

Mn7C

3

Mn5C

2

HCP

FCC

Mn23

C6

µ(M

n),

Jm

ol-1

Temperature, K

β-Mn+ γ -Mn→α-Mn p 1130 K 1097 K

L→δ-Mn+ γ-Mn e 1506 K 1508 K

L→ε-Mn+ γ-Mn e 1502 K 1518 K

γ -Mn→a-Mn+ Mn23C6 e 1031 K 1036 K

ε -Mn→ γ -Mn+ Mn23C6 e 1260 K 1260 K

ε -Mn+ Mn3C→Mn23C6 p 1293 K 1305 K

ε -Mn + Mn5C2→Mn3C p 1323 K 1325 K

ε -Mn+ Mn7C3→Mn5C2 p 1363 K 1442 K

L + Mn7C3 → ε -Mn p 1573 K 1581 K

L+CGraphite→Mn7C3 p 1604 K 1600 K

Mn3C→ Mn5C2+ Mn23C6 e 1243 K 1240 K

Mn5C2→ Mn23C6+ Mn7C3 e

10

Calculated chemical potential of Mn in various phase equilibria

This

workLiterature

Hua1990

this work

11


∆fH°298 (J/mol of atoms)

Selected experiment

values Ab initio

(T=0K)

Previous

assessment Present work

MnC 27971 251 0

Mn2C -3858 -11128 -6000

-10677(1) Mn7C3

-9100(2) -6944 -11176 -10669

-10567(1) Mn5C2

-8900(2) -6476 -10978 -10565

Mn3C -9918(1) -6993 -10094 -9911

-10716(1) Mn23C6

-8465(3) -8381 -10622 -10706

Enthalpies of formation of binary manganese carbides

(1) The effusion method-A. I. Zaitsev et al., Dokl. Phys. Chem, 395 (2004) 94(2) High-temperature reaction calorimetry-S. V. Meschel et al., J. Alloys. Compd., 257 (1997) 227(3) Adiabatic oxygen combustion calorimetry-W. M. Dawson et al., Metall. Trans, 11 (1980) 1849

12


0.0 0.1 0.2 0.3 0.4

200

400

600

800

1000

1200

1400

1600

1800

2000

Tem

per

ature

(K

)

Mole fraction C

0.0 0.1 0.2 0.3 0.4

200

400

600

800

1000

1200

1400

1600

1800

2000

[Fen2007]

[Du1989]

[Das1995]

[Ma1991]

[Kat1993]

Tem

per

ature

(K

)

Mole fraction C

800 900 1000 1100 1200 1300 1400

-16000

-14000

-12000

-10000

-8000

-6000

-4000

-2000

0

µ(M

n),

Jm

ol-1

Temperature, K

800 900 1000 1100 1200 1300 1400

-16000

-14000

-12000

-10000

-8000

-6000

-4000

-2000

0

[Ere1974]

[Du1988]

[Zai2004]

µ(M

n),

Jm

ol-1

Temperature, K

V.N. Eremenko et al., Tugo plavkie Karbidy (Russ.), G.V.

Samsonov, ed., "Naukova Dumka", Kiev, Ukr. SSR, 1970,

204


A. I. Zaitsev et al., Dokl. Akad. Nauk SSSR, 395 (2004) 632

J. Fenstad et al., Int. J. Mat. Res. 98 (2007) 10

V. Y. Dashevskii et al., Dokl. Chem. Tech. 343 (1995) 20

Z. Ma et al., Steel Res. 62 (1991) 481


Katsnelson et al., ISIJ Int., 33 (1993), 1045.

Calculated chemical potential of Mn in various phase equilibria compared with

experimental data

Calculated phase diagram of the Mn-C system compared with experimental data

13


0.00 0.05 0.10 0.15 0.20 0.25 0.30

-0.8

-0.7

-0.6

-0.5

-0.4

-0.3

-0.2

-0.1

0.0

0.1

0.2 [Kim2003]

[Tan1979]

[Kat1993]

Ln(γ

Mn)

Mole fraction C

0.00 0.05 0.10 0.15 0.20 0.25 0.30

-0.8

-0.7

-0.6

-0.5

-0.4

-0.3

-0.2

-0.1

0.0

0.1

0.2

Ln(γ

Mn)

Mole fraction C

0.00 0.05 0.10 0.15 0.20 0.25 0.30

-0.8

-0.7

-0.6

-0.5

-0.4

-0.3

-0.2

-0.1

0.0

0.1

0.2

Ln(γ

Mn)

Mole fraction C

Hua1990

this work

1628 K1673 K1723 K1773 K

Activity coefficients of manganese in Mn-C melts

E. –J. Kim. et al., Metall. Trans. B, 34 (2003) 51

Tanaka, Trans. Jpn. Inst. Met., 20 (1979), 516.


14


Activity coefficients of carbon in Mn-C melts

0.00 0.05 0.10 0.15 0.20 0.25 0.30

-2.0

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

2.0 [Kim2003]

[Tan1979]

[Kat1993]

Ln(γ

C)

Mole fraction C

Hua1990

this work

1628 K1673 K1723 K1773 K

E. –J. Kim. et al., Metall. Trans. B, 34 (2003) 51

Tanaka, Trans. Jpn. Inst. Met., 20 (1979), 516.


15


5. ConclusionThe thermodynamic description of Mn-C system has been updated in following ways:

• The Gibbs functions of the stable manganese carbides have been evaluated using recently published data of Zaitsev et al.

• The Gibbs function of the metastable Mn2C has been evaluated using enthalpy of formation obtained by ab initio calculation.

• New experimental data on the position of the liquidus line and theactivity of manganese and carbon in the Mn-C melts have been usedfor optimization of liquid phase.

The reevaluation of the phase equilibria and thermodynamic functions gives new thermodynamic description without the weaknesses of the previous one.

16


We want to thank DFG for financial support through the collaborative research centre SFB 761 “Steel - abinitio; quantum mechanics guided design of new Fe based materials"

Acknowledgement

thermodynamic re-assessment of the mn-c system · iac mse nürnberg, sep. 1-4, 2008 content 1. aim...

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