1. Journée des étudiants – REGAL
3 octobre 2016
Mirza Foisal Ahmed1, Daolun Chen2, X.-Grant Chen1
1 NSERC/Rio Tinto Industrial Research Chair
in Metallurgy of Aluminum Transformation, UQAC
2 Department of Mechanical and Industrial Engineering, Ryerson University
Effect of welding energy on microstructure and
strength of ultrasonic spot welded dissimilar
joints of aluminum to steel sheets
Effet de l'énergie de soudage sur la microstructure et
la force de la tache à ultrasons joints soudés
différents de l'aluminium pour les tôles d'acier
Introduction Results
Weight reduction in ground vehicles and
aircraft is one of the important measures to
improve fuel economy and protect the
environment. Aluminum alloys, have been and
will be increasingly used in the automotive and
aerospace industries due to their
 High strength-to-weight ratio and good
machinability
 Environmental friendliness and recyclability
To expand the use of Al alloys in automotive
body manufacturing, lower-cost joining
methods are important especially with
dissimilar joining capability.
> 5000 spot welds required to
manufacture one car
Spot Welding Technologies
RSW FSSW USW
50-100 kJ
0.15 - 0.3 s
3-6 kJ
1.0 - 5.0 s
0.6-1.5 kJ
0.25 - 0.6 s
Ultrasonic spot welding (USW) of metals is a
solid state process that produces coalescence
through the simultaneous application of
localized high frequency vibratory energy and
moderate clamping forces.
VIBRATION
Experimental Details
 To produce high-integrity joints by
dissimilar USWed Al-to-Steel joints
 To study the weld microstructure
evolution and mechanical properties of
USWed Al-to-Steel joints
 Materials compositions
Results
Chemical composition (wt.%)
Material Mn Si Cu Ni Cr Mg C P Fe Al
6061-T6 0.07 0.71 0.3 – 0.14 1.14 – – 0.18 Bal.
AISI
304
0.98 0.62 – 8.05 18.2 – 0.05 0.028 Bal. –
ASTM
A36
0.80 0.40 0.2 – – – 0.25 0.040 Bal. –
Frequency: 20 kHz
Clamping pressure: 0.41 MPa
Power: 2000 W
Time: 0.5 to 1.5 sec
Impedance setting: 8
Welding tip dimension: 8 x 6 mm
0
200
400
600
800
0 5 10 15 20 25
Intensity,Counts
Distance, μm
Al to AISI 304 Al
Cr
Fe
0
20
40
60
80
100
120
140
160
180
0 3 6 9 12 15
Intensity,Counts
Distance, μm
Al to ASTM A36
Al
Fe
0
20
40
60
80
100
0 250 500 750 1000 1250 1500 1750 2000
Max.lapshearstrength,MPa
Weld energy, J
Al to AISI 304
Al to ASTM A36
0
1
2
3
4
5
6
7
8
9
0 250 500 750 1000 1250 1500 1750 2000
Fractureenergy,kN.mm
Weld energy, J
Al to AISI 304
Al to ASTM A36
Fig. 2 Maximum tensile lap shear strength of dissimilar USWed
joints at different energy inputs.
Fig. 3 Fracture energy of dissimilar USWed joints at different
energy inputs.
0
1
2
3
4
0 250 500 750 1000 1250
Peakload,kN
Weld energy, J
IF: Interfacial failure
TTT: Transverse-through-thickness
TTT
IF
TTT
IF
0
1
2
3
4
0 250 500 750 1000 1250 1500 1750 2000
Peakload,kN
Weld energy, J
IF: Interfacial failure
TTT: Transverse-through-thickness
TTT
TTT
IF
IF
IF
IF
Fig. 4 Effect of welding energy on the tensile lap shear peak load
of dissimilar USWed joints along with typical failure modes and
locations.
What is
USW?
1.5 mm thick alloys
 Microstructure
Fig. 1 SEM back-scattered electron images with EDS line scan
positions and the corresponding EDS results at the interface of
dissimilar USWed Al 6061-T6-to-AISI 304 stainless steel and Al
6061-T6-to-ASTM A36 steel joints at a welding energy of 500 J.
 Mechanical properties
Objectives
Results
Conclusions
 Microstructure observation revealed that θ
(FeAl3) phase was mainly present at the
weld interface for both dissimilar joints.
 The average peak welding strength of Al-
to-AISI 304 stainless steel weld samples
was slightly higher than Al-to-ASTM A36
steel weld samples.
 The fracture energies of Al-to-AISI 304
stainless steel weld samples were
significantly higher as compared with Al-to-
ASTM A36 steel weld samples.
 The lap shear tensile fracture occurred
from the Al/Fe interface in the case of
lower energy inputs.
 At higher welding energy inputs, failure
mode was the transverse through-thickness
crack growth, which occurred at the edge
of the nugget zone on the softer Al side.