Electrical Resistivity Changes of High Purity Aluminum Deformed in Tension at 78K and 283K

Abstract

Single- and bi-crystal specimens of high purity aluminum were deformed in tension at 78K and 283K, and the electrical resistivity changes were measured in association with plastic deformation. The crystal orientation and testing temperature dependencies have been investigated on the single-crystal specimens. The bi-crystal specimens were studied with respect to the effect of grain boundary on the deformation. The results obtained are as follows:(1) For the bi-crystal specimens, the electrical resistivity changes show that the grain boundary effect extends to 2 or 3mm distance from the boundary at the early stage of deformation. This is consistent with the results of the slip line observations. The contribution of the grain boundary to the plastic deformation decreases with increasing strain and becomes constant after ε=10%.(2) For the single-crystal specimens, the ratio of electrical resistivity change (Δρ/ρ) does not depend on the crystal orientation at 283K, while it shows the crystal orientation dependency at 78K. The ratio (Δε78K-Δρ283K)/Δε78K also shows the crystal orientation dependency: the ratio was 50 to 60% for the specimens having a multiple slip orientation, but was less than 50% for those having a single slip orientation.(3) The orientation dependency of the τ-γ curve for single crystals was found only at 78K. This suggests that the activity of second slip system is closely connected with the thermal vibration of dislocations and the annihilation of excess vacancies, which were produced during deformation.