Euromet 2006

Influence of impurities on the melting temperature of Aluminum

Pr. B. Legendre & Dr S. Fries

EA 401

Impurities

• B, C, Cr, Cu, F, Fe, Mg, Mn, N, Ni, O, Pt

• S, Sc, Si, Ti, V, Zn.

• Al – X Optimized

• Al – Y Non optimized (or bad optimized), but the phase diagram is known

• Al – F no data

Aim

• Measurement of the slopes of the liquidus and of the solidus : = (dT/dx)

l : for the liquidus s : for the solidus

• The slope may be expressed in atomic fraction or in weight fraction.

• Determination of K :

• K = l/ s

• For Al Tfus= 660.323°C

Phase diagram

• For this subject we are interested only by a very small region in temperature and composition of binaries Al-X, but it is absolutely necessary to have a perfect knowledge of the full diagram. And to know the Gibbs function versus of T and x for each phase at a fixed pressure.

Phase diagram : Calphad Method

• A phase diagram is the graphical expression of phase equilibria, for each phase in a binary system G = f(xi, T, P)

• The limits of a two phase field are given by the common tangent of the G =f(xi)PT curves.

• For a eutectic:

• The three curves G=f(xi)p,T, have the same tangent.

•

The whole process

Cal

cula

tin

g p

has

e d

iag

ram

s

Al - Si

Al - Si

Al -Si

Al - B

Al - B

Al - B

Al - Pt

Al - Pt

Al - Pt

Al - Pt

Al - Cr

Al - Cr

Al - Ni

0

200

400

600

800

1000

1200

1400

1600

1800

TE

MP

ER

AT

UR

E_C

EL

SIU

S

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0

MOLE_FRACTION NI

THERMO-CALC (2004.09.02:15.09) :AL NI DATABASE:USER

P=1E5, N=1.,FIXED PHASES: AL3NI5=0;

2004-09-02 15:09:12.97 output by user suzana from NBMICRESS

Al - Ni

Al - Fe

Al - Fe

Al - Fe

Al - Cu

Al - Cu

Al - Cu

Al - Sc

0

200

400

600

800

1000

1200

1400

1600

TE

MP

ER

AT

UR

E_C

EL

SIU

S

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0

MOLE_FRACTION SC

THERMO-CALC (2004.09.01:15.01) :AL SC DATABASE:USER

2004-09-01 15:01:35.22 output by user suzana from NBMICRESS

Al - Sc

• No data for the solidus…

660.0

660.1

660.2

660.3

660.4

660.5

TE

MP

ER

AT

UR

E_C

EL

SIU

S

0 1 2 3 4 5 6 7 8 9 1010-5

MOLE_FRACTION SC

THERMO-CALC (2004.09.02:18.55) :AL SC DATABASE:USER

P=1E5, N=1 FIXED PHASES: BCC_A2=0;

2004-09-02 18:55:39.18 output by user suzana from NBMICRESS

Al – O: not a good optimization

655

656

657

658

659

660

661

662

663

664

665

TE

MP

ER

AT

UR

E_C

EL

SIU

S

0 1 2 3 4 5 6 7 8 9 1010-6

MOLE_FRACTION O

THERMO-CALC (2004.09.02:17.21) :AL O DATABASE:USER

P=1E5, N=1.;

3

3:X(FCC_A1,O),T-273.15

2004-09-02 17:21:42.10 output by user suzana from NBMICRESS

Al - O

• Why it is not possible to have a good optimization of the Al-O binary?

• The oxygen forms with Al an oxide which is a thin film fixed on the surface of Al and then it is a kind of protection (aluminum pans are used on the gas in a kitchen…) after the fixation of a first layer the oxygen cannot go deeper in Al. There is no homogeneity and no equilibrium.

Al - O

• L Al + Al2O3 T =~ 660°C

• Van’t Hoff law

• dln(aAl)/dT = H/RT2

• aAl ~ XAl

H = fusH(Al) = 10711.04J/mol

T = 0.452 K XAl= .9993316

• dT/dX = 676

Results

Comparison of results

Variation of the liquidus temperature versus of the

yield of impurities

• Tl = Tfus + i

• Tl = temperature of the liquidus

• Tfus temperature of fusion of pure Al

= dT/dx x : weight fractioni : yield of impurities in ppm*10-6

• Example : for Al-Cr i = 9.9*10-2ppm

= 466 Tl = 660.32°C

Temperature of liquidus and solidus for a yield of impurity

Conclusions

• It has been possible to determine the influence of impurities in Al for nearly all the selected elements.

• For O and S just an estimation has been possible.

• The most important modifications occurs with O and N

• It is possible to perform a calculation with two impurities.

Acknowledgement

• This work has been financially supported by LNE and BNM

• We are very grateful to these organisms for their contribution.

•

Al - Pt

400

600

800

1000

1200

1400

1600

1800

TE

MP

ER

AT

UR

E_C

EL

SIU

S

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0

MOLE_FRACTION PT

THERMO-CALC (2004.09.02:14.46) :AL PT DATABASE:USER

P=1E5, N=1 FIXED PHASES: L12#2=0;

2004-09-02 14:46:40.29 output by user suzana from NBMICRESS

Al - Pt

Al - Pt

659.8

659.9

660.0

660.1

660.2

660.3

660.4

660.5

660.6

660.7

660.8

660.9

TE

MP

ER

AT

UR

E_C

EL

SIU

S

0 1 2 3 4 5 6 7 8 9 1010-5

MOLE_FRACTION PT

THERMO-CALC (2004.09.02:19.20) :AL PT DATABASE:USER

P=1E5, N=1 FIXED PHASES: L12#2=0;

2004-09-02 19:20:17.48 output by user suzana from NBMICRESS

Al - Ni

659.95

660.00

660.05

660.10

660.15

660.20

660.25

660.30

660.35

660.40

TE

MP

ER

AT

UR

E_C

EL

SIU

S

0 5 10 15 20 25 30 35 40 45 5010-5

MOLE_FRACTION NI

THERMO-CALC (2004.09.02:19.14) :AL NI DATABASE:USER

P=1E5, N=1.,FIXED PHASES: AL3NI5=0;

2004-09-02 19:14:42.95 output by user suzana from NBMICRESS

Al - Pt

656

657

658

659

660

661

662

663

664

665

666

TE

MP

ER

AT

UR

E_C

EL

SIU

S

0 1 2 3 4 5 6 7 8 9 1010-3

MOLE_FRACTION PT

THERMO-CALC (2004.09.02:14.50) :AL PT DATABASE:USER

P=1E5, N=1 FIXED PHASES: L12#2=0;

2004-09-02 14:50:03.08 output by user suzana from NBMICRESS

Applications of Gibbs energies descriptionscombined to kinetic Information

Creating Gibbs energies for each phase

Al - Si