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 - Italy2Università Politecnica delle Marche, Ancona - Italy

Introduction Experiments &

Numerical Simulation Results Discussion Future Developments

Schedule (20’)

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

Intentions

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

3

33

2

M( m' n')

R

2

3

N R

L

NMm log/log'

NMn log/log'

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

Numerical SimulationTransient 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

Results - Laboratory

0

10

20

30

40

50

60

70

0 1 2 3 4 5 6 7 8 9 10equivalent strain

equ

ival

ent

stre

ss [

MP

a]

450°C 500°C550°C 575°C

1 s-1

10 s-1

0.01 s-1

AA 7020

0

10

20

30

40

50

0 5 10 15 20 25 30 35 40equivalent strain

equ

ival

ent

stre

ss [

MP

a]

450°C 500°C550°C 575°C

1 s-1

10 s-1

0.01 s-1

AA 6063

0

10

20

30

40

50

0 5 10 15 20 25 30equivalent strain

equ

ival

ent

stre

ss [

MP

a]

450°C 500°C550°C 575°C

1 s-1

10 s-1

0.01 s-1

AA 6005

Results - Laboratory

Alloy n QHW [J/mol] A [sec-1] α [MPa-1]

AA 6063 5.12 204078 6.67E+12 0.045

AA 6005A 5.16 182798 9.84E+9 0.053

AA 7020 5.37 232568 7.86E+13 0.038

n

p HWε A sinhα σ exp( Q / RT)

0.001

0.01

0.1

1

10

100

0.1 1 10

sinh(a)

450°C

500°C

550°C

575°C

AA6063

n= 5.1

a= 0.045

0.001

0.01

0.1

1

10

100

0.1 1 10

sinh(a)

450°C

500°C

550°C

575°C

AA6005

n= 5.1

a= 0.052

0.001

0.01

0.1

1

10

100

0.1 1 10

sinh(a)

Str

ain

rate

[1/

s]

450°C

500°C

550°C

575°C

AA7020

n= 5.3

a= 0.038

Results - Laboratory

1.E+10

1.E+11

1.E+12

1.E+13

1.E+14

1.E+15

1.E+16

1.E+17

1 10 100

Peak flow stress (MPa)

Z (

1/s)

AA 7020

AA6063

AA6005

Q= 206 kJ/mol

)RT/Qexp(Z HW

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

Results - Simulation

0.50.60.70.80.9

1.01.11.21.31.4

0 10 20 30Ram Displacement [mm]

Nor

mal

ized

Ram

For

ce 7020

6005A

6063

Results - SimulationTemperature Comparison

460

465

470

475

480

485

490

495

500

0 10 20 30 40 50

Extrusion Time [sec]

Tem

per

atu

re [

°C]

. 7020

6005A

6063

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.

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

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.

0 3 7 10 13 16 20 23 26 30 33 36 39 43 46 49 52 56 59 62 660

10

20

30

40

50

60

70

Hansel & Spittel

ExperimentalPredicted TransientPredicted Steady

Time [s]

RAM

For

ce [M

N]

0 5 10 15 20 2510

15

20

25

30

35

40

Experimental Theoretical

σ

ε

Results

Almax-Mori & Alumat

Alumat S.r.l.Via Lisbona 924040 Ciserano (BG)

info@alumat.it www.alumat.it

Almax-Mori S.r.l.Via Matteotti 1338065 Mori (TN)

info@almax-mori.it www.almax-mori.it