Technical Briefs

Effect of Severe Prior Deformation on Electrical-Assisted Compression of Copper Specimens

[+] Author and Article Information
Michael S. Siopis

 Mechanical Engineering, University of New Hampshire, Durham, NH 03824

Brad L. Kinsey1

 Mechanical Engineering, University of New Hampshire, Durham, NH 03824bkinsey@unh.edu

Nithyanand Kota, O. Burak Ozdoganlar

 Mechanical Engineering, Carnegie Mellon University, Pittsburgh, PA 15213


Corresponding author.

J. Manuf. Sci. Eng 133(6), 064502 (Dec 21, 2011) (5 pages) doi:10.1115/1.4005351 History: Received March 24, 2010; Revised October 21, 2011; Published December 21, 2011; Online December 21, 2011

In electrical-assisted forming (EAF), current is passed through the material during the deformation process, which results in a decrease in the required flow stress for the material. While resistive heating occurs, the flow stress reductions are beyond what can be explained by temperature effects alone. Hypotheses for this effect relate to the current affecting dislocation generation and aiding dislocation motion through the lattice structure. If the latter was the case, then materials with higher dislocation densities from severe deformation should have more pronounced benefits from EAF. In this research, Equal channel angular extrusion (ECAE) was used to induce severe plastic deformation into the material. Subsequent EAF compression experiments with the ECAE specimens and as-received material with comparable grain sizes were conducted. As expected, the EAF process reduced the flow stress value substantially more, e.g., 224 MPa versus 115 MPa at a strain of 0.8 for the ECAE specimens compared to the as-received specimens, respectively. These flow stress reductions were from a case with no current applied to a case where an initial current density of 250 A/mm2 was applied. EAF may particularly be beneficial at the microscale to address size effects as the current required to achieve an elevated current density is more viable.

Copyright © 2011 by American Society of Mechanical Engineers
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Figure 1

Samples of CuZn30 pins extruded using a Ø0.76:0.57 mm die and workpieces with grain sizes of 32 μ m and 211 μ m [1]

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Figure 2

Schematic of ECAE process [6]

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Figure 3

ECAE split die design (a) schematic and (b) picture

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Figure 4

Experimental set-up for the ECAE process

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Figure 5

Coarse grained specimen partially extruded by ECAE during the initial pass

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Figure 6

Micrographs of the coarse grained specimens extruded through the ECAE process after (a) one, (b) two, (c) three, and (d) four passes

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Figure 7

Experimental set-up for the EAF process

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Figure 8

Experimental results for as-received specimens with varying current density

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Figure 9

Reduction in flow stress at various strains for the 250 A/mm2 as-received case in comparison to the Ø1 mm 250 A/mm2 fine, medium, and coarse grained cases presented in Ref. [15]

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Figure 10

Experimental results for ECAE specimens at 0 A/mm2 and 250 A/mm2

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Figure 11

Reduction in flow stress at various strains for the 250 A/mm2 as-received and ECAE specimen cases




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