Welding of Dissimilar Materials Combinations for...
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November 10, 2011
Welding of Dissimilar Materials
Combinations for Automotive
Applications
Jerry E. Gould
Technology Leader
Resistance and Solid State Welding
ph: 614-688-5121
e-mail: [email protected]
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Metallurgical Aspects of Joining Aluminum to Steel
• Suppression of solidification defects • Suppression of Fe2Al7
• Empirically observed critical cooling times • Process selection to achieve necessary
cooling times
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0 0.05 0.1 0.15 0.2 0.25 0.3
Time (sec)
Te
mp
era
ture
(d
eg
. C
) 6061 Aluminum
1010 Steel
409 SS
Cooling characteristics of
magnetic pulse welds for a
number of materials Cooling characteristics for 0.8-mm
resistance spot welds on mild steel
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Time (sec)
Te
mp
(d
eg
. C
)
0% pene.
25% pene.
50% pene.75% pene.
100% pene.
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Mechanisms of Solid-State Bonding
2
1
Rf C
R
• Contaminant displacement/ interatomic bonding
Oxide/contaminant dissolution
Second material gettering
Metal Oxide Keq
Al Al2O3 3 10-29
Fe Fe2O3 1 10-15
Ti TiO2 1 10-01
3
* 22
*
1
1 11 exp
s
f
t Q
t R T T
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• Process characteristics
– Inertia and direct-drive friction welding variants
– Low surface velocities
– Short heating times
– Forging only in the aluminum
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Time (ms)
RP
M
Macrosection of an aluminum to steel
inertia friction weld
Deceleration profile for an inertia weld between
aluminum and steel
Friction Welding Aluminum to Steel
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Intermittent Nature of Intermetallic Formation
Intermetallic across joint
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Governing Equations Relating MPW Processing and Contact Velocities
01 2
2
2
Bkdr
dB
rdr
Bd
tIL
fnP o 2
2
2
2
2
s
s
os ttImL
fnAv 2
2
2
2
2
Maxwell equation defined in cylindrical
components
Pressure on the flier as defined by the
Maxwell equation
Flier velocity derived from the magnetic
pressure and part geometry
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Metallurgical Implications of MPW Thermal Cycles
• Cooling rates seen here comparable with other pulse welding processes – Percussion welding – Electro-spark deposition
• Rapid cooling rates imply rapid solidification – Suppression of solidification
related segregation – Reduced liquation cracking – Reduced solidification cracking
• Rapid cooling rates suppress solid state precipitation reactions – Suppression of intermetallic
phases – Reduction in solid-state-related
cracking
• Rapid cooling rates responsible for the wide range of materials joinable by MPW
Aluminum
Tungsten
1.E+03
1.E+04
1.E+05
1.E+06
1.E+07
1.E+08
1.E+09
0 10 20 30 40 50
Splat Thickness (um)
Co
olin
g r
ate
(C
/s)
Al/steel
Al/W
TI/IN625
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Resistance Welding Processes
• Resistance spot welding – Prior use of transition materials – Thermal cycles as short as 200 ms – Resolidification as bonding
mechanism – Button pullout behavior – Benefits of welding onto
galvanized steel
• Resistance butt welding – Short duration thermal cycles – Forging similar to friction welding
Direct resistance spot welds made between
1-mm Al and 0.8-mm galvanized steel sheet
Resistance butt joint between 1-mm 5754
Al and 1-mm galvanized steel sheet
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Dissimilar Metals Welding - Summary • Mechanisms of bonding for
solid-state and fusion processes
• Short thermal cycles a necessity
• Fusion and solid-state variations possible
• Suppression of intermetallics key to effective joining
• Range of candidate processing technologies demonstrated in a preliminary way
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Time (microsec)
Cu
rren
t (K
A)
induced current
Primary current
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Questions? Jerry E. Gould
Technology Leader
Resistance and Solid State Welding
ph: 614-688-5121
e-mail: [email protected]
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