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
Calculating phase diagrams
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
1800
TEMPERATURE_CELSIUS
1600
1400
1200
1000
800
600
400
200
0
0
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
MOLE_FRACTION NI
2004-09-02 15:09:12.97 output by user suzana from NBMICRESS
THERMO-CALC (2004.09.02:15.09) :AL NI
DATABASE:USER
P=1E5, N=1.,FIXED PHASES: AL3NI5=0;
Al - Ni
Al - Fe
Al - Fe
Al - Fe
Al - Cu
Al - Cu
Al - Cu
Al - Sc
1600
TEMPERATURE_CELSIUS
1400
1200
1000
800
600
400
200
0
0
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
MOLE_FRACTION SC
2004-09-01 15:01:35.22 output by user suzana from NBMICRESS
THERMO-CALC (2004.09.01:15.01) :AL SC
DATABASE:USER
Al - Sc
• No data for the solidus…
TEMPERATURE_CELSIUS
660.5
660.4
660.3
660.2
660.1
660.0
0
1
10-5
2
3
4
5
6
7
MOLE_FRACTION SC
8
9
10
2004-09-02 18:55:39.18 output by user suzana from NBMICRESS
THERMO-CALC (2004.09.02:18.55) :AL SC
DATABASE:USER
P=1E5, N=1 FIXED PHASES: BCC_A2=0;
Al – O: not a good optimization
665
3:X(FCC_A1,O),T-273.15
TEMPERATURE_CELSIUS
664
663
662
661
660
659
658
3
657
656
655
0
1
10-6
2
3
4
5
6
7
MOLE_FRACTION O
8
9
10
2004-09-02 17:21:42.10 output by user suzana from NBMICRESS
THERMO-CALC (2004.09.02:17.21) :AL O
DATABASE:USER
P=1E5, N=1.;
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 fraction
i : 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
1800
TEMPERATURE_CELSIUS
1600
1400
1200
1000
800
600
400
0
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
MOLE_FRACTION PT
2004-09-02 14:46:40.29 output by user suzana from NBMICRESS
THERMO-CALC (2004.09.02:14.46) :AL PT
DATABASE:USER
P=1E5, N=1 FIXED PHASES: L12#2=0;
Al - Pt
Al - Pt
660.9
TEMPERATURE_CELSIUS
660.8
660.7
660.6
660.5
660.4
660.3
660.2
660.1
660.0
659.9
659.8
0
1
10-5
2
3
4
5
6
7
MOLE_FRACTION PT
8
9
10
2004-09-02 19:20:17.48 output by user suzana from NBMICRESS
THERMO-CALC (2004.09.02:19.20) :AL PT
DATABASE:USER
P=1E5, N=1 FIXED PHASES: L12#2=0;
Al - Ni
660.40
TEMPERATURE_CELSIUS
660.35
660.30
660.25
660.20
660.15
660.10
660.05
660.00
659.95
0
5
10-5
10
15
20
25
30 35
MOLE_FRACTION NI
40
45
50
2004-09-02 19:14:42.95 output by user suzana from NBMICRESS
THERMO-CALC (2004.09.02:19.14) :AL NI
DATABASE:USER
P=1E5, N=1.,FIXED PHASES: AL3NI5=0;
Al - Pt
666
TEMPERATURE_CELSIUS
665
664
663
662
661
660
659
658
657
656
0
1
10-3
2
3
4
5
6
7
MOLE_FRACTION PT
8
9
10
2004-09-02 14:50:03.08 output by user suzana from NBMICRESS
THERMO-CALC (2004.09.02:14.50) :AL PT
DATABASE:USER
P=1E5, N=1 FIXED PHASES: L12#2=0;
Applications of Gibbs energies descriptions
combined to kinetic Information
Creating Gibbs energies for each phase
Al - Si