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RESEARCH PAPERS

Effect of Oxygen Content on the Processing Maps for Hot Deformation of OFHC Copper

[+] Author and Article Information
Y. V. R. K. Prasad

Department of Manufacturing Engineering and Engineering Management,  City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong

K. P. Rao

Department of Manufacturing Engineering and Engineering Management,  City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kongmekprao@cityu.edu.hk

J. Eng. Mater. Technol 128(2), 158-162 (Oct 19, 2005) (5 pages) doi:10.1115/1.2172275 History: Received February 22, 2005; Revised October 19, 2005

Processing map for the hot deformation of high purity oxygen free high conductivity (OFHC) copper (2ppm oxygen) has been developed in the temperature range 600950°C and strain rate range 0.001100s1. The map is compared with those published earlier on OFHC copper with higher oxygen contents (11ppm and 30ppm) with a view to evaluating the effect of oxygen content on the dynamic behavior of OFHC copper and the mechanism of hot deformation. The maps reveal that dynamic recrystallization (DRX) occurs over a wide temperature and strain rate range and is controlled by different diffusion mechanisms. In OFHC copper with 2ppm oxygen, the apparent activation energy for the DRX domain in the strain rate range 0.0110s1 and temperature range 600900°C is estimated to be about 137kJmole which suggests dislocation core diffusion to be the rate controlling mechanism. However, this domain is absent in the maps for OFHC copper with higher oxygen content due to the “clogging” of dislocation pipes by the oxygen atoms thereby preventing this short circuit diffusion process. At strain rates in the range 1100s1 and temperatures >700°C, the apparent activation energy is 73kJmole suggesting that DRX is controlled by grain boundary self diffusion, and this domain expands with higher oxygen content in OFHC copper. At strain rates <0.01s1 and temperatures >750°C, lattice self-diffusion is the rate controlling mechanism and this lower strain rate domain moves to lower temperatures with increasing oxygen content.

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Copyright © 2006 by American Society of Mechanical Engineers
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Figures

Grahic Jump Location
Figure 1

True stress-true plastic strain curves obtained on OFHC copper deformed in compression at 900°C at different strain rates (s−1) indicated against each curve

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Figure 2

(a) Processing map for OFHC copper (2ppm oxygen) at a strain of 0.2 showing iso-efficiency contours in a temperature-strain rate frame. The numbers against each contour represent efficiency of power dissipation in percent and are one percent apart. The dark line shows the limits for the flow instability, with the relevant regions marked as “INST.” (b) Processing map for OFHC copper (2ppm oxygen) at a strain of 0.3 showing iso-efficiency contours in a temperature-strain rate frame. The numbers against each contour represent efficiency of power dissipation in percent and are one percent apart. The dark line shows the limits for the flow instability, with the relevant regions marked as “INST.”

Grahic Jump Location
Figure 3

Processing map for OFHC copper (11ppm oxygen) at a strain of 0.3 showing iso-efficiency contours in a temperature-strain rate frame (from Ref. 4). The numbers against each contour represent efficiency of power dissipation in percent and are one percent apart. The dark line shows the limits for the flow instability, with the relevant regions marked as “INST.”

Grahic Jump Location
Figure 4

Processing map for OFHC copper (30ppm oxygen) at a strain of 0.3 showing iso-efficiency contours in a temperature-strain rate frame (from Ref. 4). The numbers against each contour represent efficiency of power dissipation in percent and are one percent apart.

Grahic Jump Location
Figure 5

Plot showing the variation of n×(logarithm of normalized flow stress) with inverse of test temperature at different strain rates obtained from the data on OFHC copper with different oxygen contents

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