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21/06/2016 1
Explosive welding of aluminium and copper:
effect of the base plate material
Gustavo Senna Carvalho - PhD. Student at University of Coimbra
XIII International Symposium on Explosive Production of New Materials: Science, Technology, Business, and Innovations
G. Carvalho, R. M. Leal, I. Galvão, R. Mendes, J. B. Ribeiro and A. Loureiro
Joining different materials
2
Joining by welding STRATEGIC
Replace connectors rivets and bolts Weight reduction
ENERGY / FUEL ECONOMY
Joining different materials it’s a necessity!
StrengthCorrosion resistance
Low weight
Thermal conductivity
COMPONENT
Costs of materials!
Electrical conductivity
Copper - aluminium joining
3
Interesting joining
Applications / Industries
Copper and aluminium are two of the three most used metals on earth
TransportationElectrical
Material transitionsRefrigeration
industry
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Copper - Aluminium joining
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MATTHEWS, S. J., et al. (1997) Dissimilar Metals in “AWS Welding Handbook – Metals and Their Weldability” Cap 12. American Welding Society EUA.
Copper Aluminium
Melting temperature 0.7 0.4
Thermal expansion 1.5 2.1
Thermal conductivity 5.9 3.1
Physical properties of Cu and Al with steel as reference (1.0)
Differences in:
Melting temperature
Thermal conductivity
Thermal expansion
Difficult combination!
Metallurgical problems: hot cracks
Heat directed at only one of the materials
High residual stresses
Solid-state welding (EXW) for Cu-Al joining
5
Possibility of localized fusion and some diffusion is almost inevitable in this process.
High temperature (lower than fusion processes)
Pressure
Plastic deformation
Intimate contact between the materials
ATOMIC DIFFUSION
EXW is a viable way to join this combination but it’s not easy because of the
formation of brittle intermetallic phases and defects related to localized fusion.
Differences in melting temperature
Dissimilar welding
POSSIBILITY OF LOCALIZED MELTING
Copper
Aluminium
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The diffusion issue
DRITS, M.E., BOCHVAR, N.R., GUZEI, L.S., LYSOVA, E.V., PADEZHNOVA, E.M., ROKHLIN, L.L., TURKINA, N.I., (1979) Cu-Al in “Binary and Multicomponent Copper-Base Systems” [in Russian], p.8. Ed. Nauka. Moscou, União Soviética.
Formation of brittle intermetallic phases.
Harmful to the mechanical properties.
Explosive Welding - EXW
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Explosion welding is a solid-state process characterized by a high-velocityimpact between two materials as the result of controlled detonation of anexplosive.
Vd
β Stand-off distanceFlyer plate
Base plate
Explosive
Vc
Vp
Jet
Direction of welding
Objectives
8
The purpose of this investigation was to compare welds with differentbase plate alloys and the same flyer alloy: a similar Cu-Cu weld and adissimilar Cu-Al weld. Both partially overlapped.
AA6082-T6 base plate
Cu-DHP flyer
Cu-DHP base plate
Cu-DHP flyer
SIMILAR WELD DISSIMILAR WELD
Support for the flyer
Objectives
9
The purpose of this investigation was to compare welds with differentbase plate alloys and the same flyer alloy: a similar Cu-Cu weld and adissimilar Cu-Al weld. Both partially overlapped.
F
F
For load transfer applications
Materials and Conditions
10
SAME WELD PARAMETERS
Explosive composition and density STD plates thickness
Ammonium nitrate-basedexplosive emulsion + withhollow glass microspheres
Flyer (Cu): 1 mmBase plate : 3mm
1,35 mm
DIFFERENT MATERIALS
Different base plates
AA 6082-T6 Dissimilar weld
Cu-DHP (C12200) Similar weld
RESULTS
11
Results – Interface analysis - Microstructure
12
Similar: Copper Copper
Wavy interface
Results – Interface analysis - Waves
13
Melded zones
Melded zones
Results – Interface analysis - Microstructure
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Dissimilar: Copper Aluminium
No waves!Plane interface
Interface with “weak etch”
New phase formed at the interface
Results – Interface analysis - Microstructure
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Dissimilar: Copper Aluminium
Intermetallic compound
Results – Interface analysis - Microstructure
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Dissimilar: Copper Aluminium [SEM analysis]
68.94 %at. Al30.63 %at. Cu
CuAl2
Al
Cu
Results – Interface analysis - Hardness
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The hardness increased for both samples, but it can be seen a slightly greater increase in for the Cu-flyer of the similar weld
60
80
100
120
140
Har
den
ess
[H
V0
.2]
Distance to interface [mm]
Cu-Al Cu-CuFlyer Base Plate
Al
Cu
-1.0 -0.5 0.0 0.5 1.0 1.5 2.0
Discussion
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Waves for the combination Cu-CuNo waves for the combination Cu-Al
Yield strength
Differences in Yield strength
Wave formation
Wave formation is strongly related with the “Yield
Strength” and “density” of the base plate and flyer
Melted regions but no intermetallics Cu-Cu WeldPresence of intermetallic phase Cu-Al Weld
Expected
Conclusions
19
• Was possible to joining both samples with the same parameters;
• Increase in hardness for both welds but a slightly greater increasein hardness for the Cu-flyer of the similar weld;
• Despite the same parameters, it was found different interfacemorphologies due differences on the base plate Yield Strength anddensity;
• Formation of intermetallic phases for the Cu-Al combinationrelated with diffusion of copper to the aluminium plate.
THANK YOU!OBRIGADO!
20
“Paço das Escolas” University of Coimbra