Paper presentated by Eng. Tommaso Pinter (Alumat & Almax Grosup) at ET12 - Miami 2012. Content: Necessity to Predict Aluminium Flow & Tool Stress Poor Availability of Constitutive Equations Need of Hot Torsion Tests to provide Constitutive Parameters to implement in FEM codes Validate Constitutive Equations using Industrial Applications

1. TENTH INTERNATIONAL ALUMINUM EXTRUSION TECHNOLOGY
SEMINAR AND EXPOSITION
Constitutive Equations for Hot
Extrusion of AA6005A, AA6063
and AA7020 Alloys
Tommaso Pinter1
Mohamad El Mehtedi2
1Almax Mori S.r.l., Mori - Italy
2Università Politecnica delle Marche, Ancona - Italy

2. Schedule (20’)
 Introduction
 Experiments & Numerical
Simulation
 Results Discussion
 Future Developments

3. Intentions
 Necessity to Predict Aluminium Flow &
Tool Stress
 Poor Availability of Constitutive Equations
 Need of Hot Torsion Tests to provide
Constitutive Parameters to implement in
FEM codes
 Validate Constitutive Equations using
Industrial Applications

4. Torsion Tests
 DC homogenized billets courtesy
of Nedal Aluminium B.V.
 Specimens r=4mm
 Pre-Heating: 1 Ks-1 (5 minutes)
 έ= 0.01-1-10s-1
 T=450-500-550-575 C
 Water Quenching at ε=30
3M 2 N R
 ( 3  m'  n') 
2  R3 3L

m'   log M /  log N
n'   log M /  log N

5. Extrusion
 Why? To establish BCs for numerical simulations
and validate the FEM model
 How? 50MN (11’’) direct press by ETEM S.A.
 What? Transport Profile in AA6005
 Extrudate Temperature: 550-560 C
 RAM force required: 91% press capacity

6. Numerical Simulation
Transient simulation (51 seconds)
with 30 variable time steps for a total
CPU time 76 hours.
 T Workpiece: 460 C
 Billet Taper: 20 C/m
 T Die: 480 C
 T Container: 430 C
 Ram Speed: 3 mm/s
 HTC die/workpiece: 500 W/m2K
 HTC container/billet: 3000 W/m2K

7. Results - Laboratory
50 50
AA 6063 450°C 500°C AA 6005 450°C 500°C
550°C 575°C 550°C 575°C
40 40
equivalent stress [MPa]
equivalent stress [MPa]
10 s -1 10 s -1
30 30
20 20
1 s -1
10 0.01 s -1 10 1 s -1
-1
0.01 s
0 0
0 5 10 15 20 25 30 35 40 0 5 10 15 20 25 30
equivalent strain equivalent strain
70
AA 7020 450°C 500°C
60 550°C 575°C
equivalent stress [MPa]
50 10 s -1
40
1 s -1
30
20
10 0.01 s -1
0
0 1 2 3 4 5 6 7 8 9 10
equivalent strain

8. Results - Laboratory
100 100 100
AA7020 AA6005 AA6063
10 450°C 10 10 450°C
450°C
500°C 500°C 500°C
Strain rate [1/s]
550°C 550°C 550°C
1 1 1
575°C 575°C 575°C
a= 0.038 a= 0.052 a= 0.045
0.1 0.1 0.1
0.01 n= 5.3 0.01 n= 5.1 0.01 n= 5.1
0.001 0.001 0.001
0.1 1 10 0.1 1 10 0.1 1 10
sinh(a) sinh(a) sinh(a)
Alloy n QHW [J/mol] A [sec-1] α [MPa-1]
ε  A  sinh α σ p  exp( QHW / RT)
AA 6063 5.12 204078 6.67E+12 0.045 n
AA 6005A 5.16 182798 9.84E+9 0.053

AA 7020 5.37 232568 7.86E+13 0.038

9. Results - Laboratory
1.E+17
AA 7020
1.E+16
AA6063
AA6005
1.E+15
Q= 206 kJ/mol
1.E+14 Z   exp( QHW / RT )

Z (1/s)
1.E+13
1.E+12
1.E+11
1.E+10
1 10 100
Peak flow stress (MPa)

10. Results - Simulation
 Good correspondence of
Temperature and profile
Deformation
 RAM force overestimated (flow
stress not dependent on strain)
 Extrudability Data were
normalized in respect of AA6005A
peak force

11. Results - Simulation
Ram Forces normalized with 6005A peak force
1.4
1.3 7020
Normalized Ram Force
1.2 6005A
1.1 6063
1.0
0.9
0.8
0.7
0.6
0.5
0 10 20 30
Ram Displacement [mm]

12. Results - Simulation
Temperature Comparison
500
.
7020
495
6005A
Temperature [°C]
490
6063
485
480
475
470
465
460
0 10 20 30 40 50
Extrusion Time [sec]

13. Discussion
 The peak stress values of the AA6005 alloy are close to
AA7020 for low Z-values, while in the high-Z regime, the
stresses were closer to the AA6063 values.
 The simulation results show that to extrude the same
profile in alloy AA6063, a ram force 17% lower than that
used in AA6005, is required.
 The implementation in FEM codes of a relationship where
flow stress (σ) is dependent on the strain (ε) seems
mandatory to properly predict the die behavior under
working conditions.

14. Future Developments
 Implement an ε dependent constitutive
equation (Hansel – Spittel)
 Validate the model in respect of the Ram
Force Vs Time
 Simulate the real pressure map on the tool
 Give accurate indication of die stress

15. New Equations in HX
In the Hansel-Spittel equation the flow stress () dependence
on strain and strain rate is described by the expression:
where A and mi are material parameters and T is the absolute
temperature.
The first 8 coefficients and A were calculated thanks to a linear
regression of all the flow stress experimental data obtained for
alloy AA6005A while m9 has been settled equal to zero.

16. Experimental Theoretical
40
Results
35
30
25
ε
20
15
Hansel & Spittel 10
70 0 5 10 15 20 25
σ
60
50
RAM Force [MN]
40
Experimental
30
Predicted Transient
20 Predicted Steady
10
0
0 2 5 8 101215172022252730323437394244474952545759626466
Time [s]

17. Almax-Mori & Alumat
Almax-Mori S.r.l. Alumat S.r.l.
Via Matteotti 13 Via Lisbona 9
38065 Mori (TN) 24040 Ciserano (BG)
info@almax-mori.it info@alumat.it
www.almax-mori.it www.alumat.it