1Nikko Copper Works, The Furukawa Electric Co.,Ltd., Nikko
It is a very interesting problem of whether or not the dislocation arrangement having the same effects as those of groups of piled-up dislocations or piled-up dislocations are produced due to straining irrespective of single or polycrystalline copper. With the aim of solving this problem, the author carried out an observation of the etch pits and slip bands, and examined the deformation mechanisms of polycrystallin copper. The observation of the etch pits showed rows of pits which could be consider to be groups of dislocations which piled up against the grain boundaries, and rows of pits which were arranged crystallographically. It is doutful whether the individual etch pit corresponds to the individual dislocation. However, in view of the fact that the slip bands, in general, reach the grain boundaries at the length almost equal to the diameter of the grain, it can be thought that the dislocations pile up against the grain boundaries, and that such a phenomenon play an important role in the strain hardening of polycrystalline copper. The deformation of polycrystalline copper to strain is classified into the following three ranges:
(1) ε < ∼ 0.1%
The range in which dislocations pile up against the grain boundaries.
(2) ∼ 0.1% < ε < ∼ 1%
The range in which the number of dislocation in rows increase.
(3) ε > ∼ 1%
The range in which multiple slips occur.
Furthermore, cross slip of sliding dislocations caused by the stress field of groups of piled-up dislocations is known to play an important role as the source of dislocations.
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