The electrical resistivity of dislocations in aluminium.

Aluminium foil was extended by tensile deformation at room temperature by amounts up to about 15% plastic strain. The flow stress (alpha) the change in electrical resistivity (Deltarho) and the dislocation density (N[1]) were measured as a function of plastic strain and subsequent annealing. The change in electrical resistivity was measured at liquid Helium temperature and the dislocation density was measured by thin film transmission electron microscopy. The change in electrical resistivity and the dislocation density were both proportional to the plastic strain and hence to one another. The annealing of the extended specimens was found to occur in three stages. The first, which occurred at room temperature was due to the annealing out of point defects; an activation energy of 0.65eV was obtained for this process. The second stage took place above about 70°C and during this process both a re-arrangement and loss of dislocations occurred. The third stage was recrystallisation. The resistivity of dislocations in the deformed state was found to be: Deltarho = (18 +/- 1) X 10[-20] N[1] ohm cm. and after the second annealing stage: Deltarho = (17 +/- 2) X 10[-20] N[1] ohm cm. These results have been compared with experimental values obtained by other authors and with various theoretical estimates. It is suggested, that the loss of dislocations during the preparation of thin foils was negligible, that the scattering of conduction electrons by the core of a dislocation compared with that of the long range strain field was not negligible in contributing to the electrical resistivity and that the theoretically calculated value of the stored energy of a dislocation in Aluminium[38] was correct within +/- 25%