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Research Papers

An Investigation of Magnetic Pulse Welding of Al/Cu and Interface Characterization

[+] Author and Article Information
Xin Wu

Mem. ASME
Mechanical Engineering,
Wayne State University,
Detroit, MI 48202
e-mail: xwu@eng.wayne.edu

Jianhui Shang

Mem. ASME
Hirotec America,
Auburn Hills, MI 48326
e-mail: jshang@ewi.org

1Corresponding author.

2Present address: Edison Welding Institute, Columbus, OH 43221.

Contributed by the Manufacturing Engineering Division of ASME for publication in the JOURNAL OF MANUFACTURING SCIENCE AND ENGINEERING. Manuscript received February 8, 2013; final manuscript received June 24, 2014; published online August 6, 2014. Assoc. Editor: Wei Li.

J. Manuf. Sci. Eng 136(5), 051002 (Aug 06, 2014) (11 pages) Paper No: MANU-13-1052; doi: 10.1115/1.4027917 History: Received February 08, 2013; Revised June 24, 2014

This paper investigated the effect of magnetic pulse welding (MPW) condition (welding power, surface scratches, and contamination) on the establishment of welding between aluminum and copper tubes, and the associated welding mechanisms. The results showed that higher applied power and surface scratches in tangential direction were in favor for good weld, and oil on the surface prevented welding. Direct evidences were obtained on local interface melting under a high welding power. CuAl intermetallics with different atomic ratios were identified by energy dispersion spectrum (EDS) chemical analysis and by microscratching test. The mechanisms of MPW and the process improvement were discussed.

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Copyright © 2014 by ASME
Topics: Welding , Melting
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References

Figures

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Fig. 1

The electromagnetic system (a) and its assembly schematics (b), consisting of an electrical coil (c), a field concentrator made of copper (d), the tubular workpieces Al (e), and Cu with special end geometry (f)

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Fig. 4

Selected images of sectioned samples under three applied voltages, and the binary images of Cu and Al used for strain calculation

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Fig. 5

The distributions of the true strain components along the axial distance from Cu head end (at x = 0) to Al tube free end (at x = 20 mm), for Al (a) and Cu (b) at 5.2 kV. Also shown are the effective strains for Al and Cu for this specimen (c), and for the specimens welded at different voltages and surface preparation conditions (d). The plastic works (e) and the bonded length fraction (f) are plotted for different welding voltages.

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Fig. 3

The measured current wave for welding at 5.2 kV (a), and the resulting specimen cross section (b) showing diameter reduction of Al and Cu, and the peeled fracture surface (c) showing very rough aluminum inner surface, indicating strong bonding and ductile fracture within Al

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Fig. 7

A sectioned sample welded at 6.0 kV (top), and the microstructures over the three consecutive segments L1, L2, and L3 from left to right

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Fig. 8

Interfaces of the sample with the original copper surface sanded in axial direction. No correlation of the failed interface edge and the original lathe-turned pitch can be identified.

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Fig. 9

New compound phase formed at the welding interface region that mixes with base materials (a) and (b), and contains microcracks (b), observed under optical microscope; incomplete intermetallic phase formation at a wavy pocket is seen in (c), with the Al wave front converted to intermetallic but the tail still remained as base Al

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Fig. 15

The Al–Cu binary phase diagram, computed with commercial software and with available thermodynamics database

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Fig. 14

Scratch test with the use of Vicker's indenter and operated at 120 gf and 2 μm/s, with one of the diagonal axis aligned along the moving direction. The circled area contains a few microcracks.

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Fig. 10

The optical micrograph of a sample welded at 6.0 kV, and a round pore with a smooth surface was observed (a). By refocusing at the pore bottom (b) some surface cracks were revealed.

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Fig. 11

The sample welded under 6.0 kW power (a), with three local melting zones shown in (b) and (c) as evident by the smooth glassy pore surfaces with cracks; (d) the local enlargement of one pore shown in (b).

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Fig. 12

SEM micrographs of two interface regions and their local enlargements. The rough Cu surface was from chemical etching.

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Fig. 13

SEM–EDM chemical analysis on two samples, along the lines crossing the interface (top), and the copper atomic percentage distribution along the scanned line spots (bottom)

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