抄録
A series of experiments has been carried out by the present authors by means of the Berg-Barrett method, the etch-pit technique, and transmission electron microscopy to make clear the substructure developed in copper single crystals during high temperature creep. In this paper the results obtained on the dislocation structures by transmission electron microscopy are reported. The dislocation motion and the creep rate in steady-state creep is also discussed on the basis of the experimental results. The main conclusions obtained are as follows:
(1) The subgrains surrounded by “large angle sub-boundaries” observed by the Berg-Barrett method and the etch-pit technique are further divided into smaller ones by “small angle sub-boundaries” which can be detected only by transmission electron microscopy.
(2) In steady-state creep mobile dislocations are emitted mainly from the small angle sub-boundaries. After gliding through subgrains, the mobile dislocations are absorbed into the neighbouring small angle sub-boundaries to become immobile. The mean free path of the mobile dislocations is thus limited by the small angle sub-boundaries, being a few μ to 10 μ and 10 μ to a few tens of microns for the primary edge and the primary screw dislocations, respectively.
(3) Steady-state creep rates can be explained quantitatively from the results by transmission electron microscopy, on the assumption that the glide motion of screw dislocations having super jogs is the rate-controlling process. The heights of the super jogs are ∼20 b and ∼6 b and their spacings are ∼0.4 μ and ∼0.2 μ at 745°C and 610°C, respectively.
