interface structural analysis of similar and dissimilar magnetic pulse welded joints ·...

R. Raoelison, M. Rachik, N. BuironR. Raoelison, M. Rachik, N. BuironR. Raoelison, M. Rachik, N. BuironR. Raoelison, M. Rachik, N. Buiron

Interface structural analysis of similar and dissimilar magnetic pulse welded joints

Laboratoire Roberval, Université de Technologie de Compiègne UTC, France

Workshop Impulse forming & joiningWorkshop Impulse forming & joiningWorkshop Impulse forming & joiningWorkshop Impulse forming & joining

IBS Belgium, 7IBS Belgium, 7IBS Belgium, 7IBS Belgium, 7----8 may 20138 may 20138 may 20138 may 2013

Project MSIM (2010-2012):

Funded by Région Picardie

MOTIVATIONMOTIVATIONMOTIVATIONMOTIVATION

Development of multi-material assembly for lightweight structures → MPW : joining solution

Optimization of the MPW → improvement of durability and reliability of dissimilar-material assemblies

Current challenge Current challenge Current challenge Current challenge :

Project MSIM Project MSIM Project MSIM Project MSIM :

Driving the MPW toward its optimal ability for an efficient welding of dissimilar-material assemblies

• Analysis of the interaction process parameters/joint quality• Analysis of the effect of metal dissymetry on the joint quality• Modeling and computational simulation of the MPW

----1111----


present results : weld quality depending on the present results : weld quality depending on the present results : weld quality depending on the present results : weld quality depending on the process parametersprocess parametersprocess parametersprocess parameters

• Modeling and computational simulation of the MPW• Feasibility study and development of tooling

Experimental approach :Experimental approach :Experimental approach :Experimental approach :

• characterization and classification of the different joints encountered

• relation between weld quality and process parameters

• weldability study of Al/Al and Al/Cu assemblies

Material and methodMaterial and methodMaterial and methodMaterial and method----2222----

Comparison between two cases of assemblyComparison between two cases of assemblyComparison between two cases of assemblyComparison between two cases of assembly :

Similar materials : Al6060T6/Al6060T6

Dissimilar materials : Al6060T6/Cu

Material chemical composition (% weight)

Material properties

Welding test investigated with identical parameter sets

σ (Ωm)-1 Tf(°C) ρ(kg/m3) E(GPa) G(GPa) Rm(MPa) Rp (MPa) Ar(%) Hv

Mg Si Fe Mn Cr Zn Ti Cu Al

Al6060T6 0,8-1,2 0,4-0,8 0,7 0,15 0,04-0,35 0,25 0,15 0,15-0,4 Balance

Cu - - - - - - - 99,9 -

Geometrical characteristic of the samples

d D

L

Flyer :

D=25mmd=22mmL= 50mm

Target :d2

d1

l1 l2 d1

l1= 21mmd2

l2= 23mm

σél(Ωm)-1 Tf(°C) ρ(kg/m3) E(GPa) G(GPa) Rm(MPa) Rp0,2(MPa) Ar(%) Hv

Al6060T6 2,5.107 650 2,7.103 70 26,6 290 240 10 80

Cu 5,8.107 1065 8,9.103 124 46,6 250 200 14 80

→ dimensional characterizationdimensional characterizationdimensional characterizationdimensional characterization

Characterization of the jointCharacterization of the jointCharacterization of the jointCharacterization of the joint

Peel test

Torsion-shear test

StressStressStressStress

StressStressStressStress

WeldWeldWeldWeld

weldweldweldweld

→ deviation of the failure

→ failure at the interface

weld

----3333----

Inner tube

Flyer Weld

Compression

Microstructure examination

→ structural characterizationstructural characterizationstructural characterizationstructural characterization

16mm

→ mechanical characterizationmechanical characterizationmechanical characterizationmechanical characterization

Push-out test


Joint characteristicsJoint characteristicsJoint characteristicsJoint characteristics

Dimensional characterizationDimensional characterizationDimensional characterizationDimensional characterization

Unwelded interface Beginning of bonding (trace of residue)

Beginning of good welding (thin weld)Large weld

Striation : circular path due to interfacial deformation → ductile and potentially permanent weld

Structural characterizationStructural characterizationStructural characterizationStructural characterization

----4444----

Structural characterizationStructural characterizationStructural characterizationStructural characterizationBeginning of bonding Beginning of good welding Potentially permanent weld

Interface

SubGB

Emergence of slip band

EBSD analysis


→ grain deformation (strong)

EBSD analysisEBSD analysisEBSD analysisEBSD analysis

TEM analysis TEM analysis TEM analysis TEM analysis Interface

Sub grain

Slip band

Interface featuresInterface featuresInterface featuresInterface features TEM analysisTEM analysisTEM analysisTEM analysis

----5555----Multiscale characterization of the Al/Al jointMultiscale characterization of the Al/Al jointMultiscale characterization of the Al/Al jointMultiscale characterization of the Al/Al joint

TEM analysis of the interface :

high density of dislocation

grain size (< 500nm) → modification of the mecanichal properties

Nanoidentation → gradient of hardness

(Hv interface ≈1.5*Hv base metal)


Further SEM analysisFurther SEM analysisFurther SEM analysisFurther SEM analysis

- creation of cavities (heterogeneous material structure ) : decohesion at the phases interface

- création of cavities from inclusion : matrice/inclusion decohesion (e.g. due to precipitates)

Al6060T6 material : with AlAl6060T6 material : with AlAl6060T6 material : with AlAl6060T6 material : with Alxxxx----MgMgMgMgyyyy----SiSiSiSiz z z z precipitatesprecipitatesprecipitatesprecipitates

Formation of the dimple :

----6666----Fractal analysis of the Al/Al jointFractal analysis of the Al/Al jointFractal analysis of the Al/Al jointFractal analysis of the Al/Al joint

- observation of spheroïdal inclusion inside ome dimples -EDX analysis of the inclusion : diffraction of Al and Mg

→ development of dimple: potentialydue to precipitates


MET analysis of the Al/Al jointMET analysis of the Al/Al jointMET analysis of the Al/Al jointMET analysis of the Al/Al joint

Base metal :

→ matrix of Al → needle shape precipitate

Interface :

→ needle shape p/tes dissapear → spheric p/tes appear

Structural analysis of the precipitatesStructural analysis of the precipitatesStructural analysis of the precipitatesStructural analysis of the precipitates

----7777----

→ spheric p/tes appear

Fractal analysis Fractal analysis Fractal analysis Fractal analysis

→ creation of macro-cavities (crack initiation sites)

----8888----Analysis of defective Al/Al joint Analysis of defective Al/Al joint Analysis of defective Al/Al joint Analysis of defective Al/Al joint

→ regular distribution of humps → porous zone within the hump


SEM examination of the porous pockets and mechanichal effectSEM examination of the porous pockets and mechanichal effectSEM examination of the porous pockets and mechanichal effectSEM examination of the porous pockets and mechanichal effect ----9999----

Local analysis of the porous zonesLocal analysis of the porous zonesLocal analysis of the porous zonesLocal analysis of the porous zones→ porosity with high density (attributable to cavitation)porosity with high density (attributable to cavitation)porosity with high density (attributable to cavitation)porosity with high density (attributable to cavitation)

0

5

10

15

20

0 0,5 1 1,5 2 2,5

Ucolumn(mm)

F(kN)

Large weldThin weldWeld with voids

Effect on the mechanical behaviour Effect on the mechanical behaviour Effect on the mechanical behaviour Effect on the mechanical behaviour

Effect of material dissymetry Effect of material dissymetry Effect of material dissymetry Effect of material dissymetry : effect on the weld featureseffect on the weld featureseffect on the weld featureseffect on the weld features

Al/AlAl/AlAl/AlAl/Al

→ Formation of intermetallic phase

U=6.5kV,g=1.5mmU=6.5kV,g=1.5mmU=6.5kV,g=1.5mmU=6.5kV,g=1.5mm

U=6.5kV,g=1.5mmU=6.5kV,g=1.5mmU=6.5kV,g=1.5mmU=6.5kV,g=1.5mmAl/CuAl/CuAl/CuAl/Cu

----10101010----

→ continuous layer or discontinous pockets


EDS and TEM analysis Diffraction in the Al part

Diffraction in AlnCum

→ ordered structured

→ crystal lattice

Structural analysis of the intermetalic phaseStructural analysis of the intermetalic phaseStructural analysis of the intermetalic phaseStructural analysis of the intermetalic phase ----11111111----

IntermetalicIntermetalicIntermetalicIntermetalic :

→ complex structure

→ random distribution

→ extremely fine grains

amorphous phase amorphous phase amorphous phase amorphous phase

formation by hyperquenchingformation by hyperquenchingformation by hyperquenchingformation by hyperquenching(quick cooling : 104-106K/s )


----12121212----Further characterization of the intermetallic phaseFurther characterization of the intermetallic phaseFurther characterization of the intermetallic phaseFurther characterization of the intermetallic phase

0

5

10

15

20

0 1 2 3

Ucolumn (mm)

F (kN)

Al/Al thin weld

Al/Cu thin weld

brittle fracture of the interface

→ porous structure (size of ~ hundreds nm)

→ fracture surface : rupture by fragmentation

Mechanical behaviour Mechanical behaviour Mechanical behaviour Mechanical behaviour

Amorphe phase : britle weldAmorphe phase : britle weldAmorphe phase : britle weldAmorphe phase : britle weld

----13131313----Further mechanical Further mechanical Further mechanical Further mechanical characterizationcharacterizationcharacterizationcharacterization of the of the of the of the intermetallic intermetallic intermetallic intermetallic phasephasephasephase

Intermetallic Intermetallic Intermetallic Intermetallic layer layer layer layer

0

50

100

150

200

250

300

0.00 0.50 1.00 1.50 2.00 2.50 3.00

F (

mN

)

penetration (µµµµm)

Intermetallic

Base Metal

IntermetallicIntermetallicIntermetallicIntermetallic → no plastic deformation surrounding the indent, increase of the hardnessno plastic deformation surrounding the indent, increase of the hardnessno plastic deformation surrounding the indent, increase of the hardnessno plastic deformation surrounding the indent, increase of the hardness

Force / displacement indentation curve Force / displacement indentation curve Force / displacement indentation curve Force / displacement indentation curve Base Metal Base Metal Base Metal Base Metal

plastic plastic plastic plastic deformationdeformationdeformationdeformation

Hv int/lic = 1.9 GPa, Hv BM=1,5 GPa Hv int/lic = 1.9 GPa, Hv BM=1,5 GPa Hv int/lic = 1.9 GPa, Hv BM=1,5 GPa Hv int/lic = 1.9 GPa, Hv BM=1,5 GPa E int/lic = 77 GPa, E BM= 63 GPA E int/lic = 77 GPa, E BM= 63 GPA E int/lic = 77 GPa, E BM= 63 GPA E int/lic = 77 GPa, E BM= 63 GPA

0

1

2

3

4

5

U(kV)

g(mm)

perennial weld (2mm<ww<7mm) ring-shaped weld (1.5mm<ww<2mm) bad weld

Brittle weld

Effect of metal dissymetryEffect of metal dissymetryEffect of metal dissymetryEffect of metal dissymetry


Welding rangeWelding rangeWelding rangeWelding range Comparison of Comparison of Comparison of Comparison of achieved good weldachieved good weldachieved good weldachieved good weld

Large residueLarge residueLarge residueLarge residue


Al/CuAl/CuAl/CuAl/Cu

Short length residueShort length residueShort length residueShort length residue

----14141414----

00 1 2 3 4 5 6 7 8 9

0

1

2

3

4

5

0 1 2 3 4 5 6 7 8 9

U(kV)

g(mm)

thin weld (ws~2mm) ring-shaped weld (0.1mm<Ws<2mm) bad weld Brittle weld

Brittle weld

Al/CuAl/CuAl/CuAl/Cu reduction

Illustration of Al/Cu weld above Illustration of Al/Cu weld above Illustration of Al/Cu weld above Illustration of Al/Cu weld above the upper limit (brittle weld)the upper limit (brittle weld)the upper limit (brittle weld)the upper limit (brittle weld)

(case with U=7.5kV, g=4mm)


ConclusionsConclusionsConclusionsConclusions

• interface structural analysis of a similar AA6060T6 weld :

•weld enable to undergo plastic deformation•potentialy permenant weld: ductile with a wavy interface•welded interface with high density of dislocations and nanograin•heat effected interface : disappearance of needle shape precipitate and formation of new sheroidal ones •formation of defective weld with voids and porous zone

----15151515----

→ combination of Al6060T6/Cu : not good for the interface integrity

reduction of the weldability range

•formation of CuaAlb intermetallic phase •intermetallic : → discontinous pocket or continous layer

→ amorphous phase and/or with nanograin→ phase with nanovoids→ brittle and low resistant weld

• interface structural analysis of a dissimilar AA6060T6/Cu weld :


1. RAOELISON R., BUIRON N., RACHIK M., HAYE D., FRANZ G., HABAK M., ‘Study of the elaboration of a practical weldability window in magnetic pulse welding’, Journal of Materials Processing Technology (2013) http://dx.doi.org/10.1016/j.jmatprotec.2013.03.004.

2. RAOELISON R., BUIRON N., RACHIK M., HAYE D., FRANZ G., ‘Efficient welding conditions in magnetic pulse welding process’, Journal of Manufacturing Process, 14(2012), 372-377.

3. RAOELISON R., BUIRON N., RACHIK M, ‘Investigation of material dissymetry effect on magnetic pulse welding of Al/Cu assembly: effect of intermetallic on the weld characteristic and the weldability’, (to be submitted).

Related papers

and the weldability’, (to be submitted).

4. RAOELISON R., BUIRON N., RACHIK M., HAYE D., FRANZ G., ‘Assessment of Gap and Charging Voltage Influence on Mechanical Behaviour of Joints Obtained by Magnetic Pulse Welding’, Proceedings of the 4th International Conference of High Speed Forming, Germany 2012, 207-216.

5. RAOELISON R., BUIRON N., RACHIK M., HAYE D., HABAK M., ‘Elastoplastic and Damage Behaviour of Magnetic Pulse Weld Interfaces’, Proceedings of the 10th International Conference on Technology of Plasticity, Aachen, Germany, p. 1160-1163, 2011

interface structural analysis of similar and dissimilar magnetic pulse welded joints ·...

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