Effects of cold-working on low-temperature electrical resistivity of aluminium

Abstract

The purpose of this research was to make clear the effects of cold-drawing, particularly of medium and heavy cold working, upon the electrical resistivity of metal. Two kinds of commercially pure aluminium, the nominal grades of 99.9% and 99.99% purity were used. The measurements of the electrical resistivity were made at -196°C using the specimen of 1m in length and 1mm in dia.In the diagram of the relation between the electrical resistivity and the reduction of the section area, the electrical resistivity was, in its maximum at the point of about 40% reduction and in its minimum at 70%. And yet the discrepancy between the maximum and minimum value was small. When the reduction was over 80%, the resistivity increased abruptly. The curves obtained for both grades of aluminium were quite similar.This research was not a completely quantitative one, because we could not clarify the structural changes of the crystal lattices according to the varied stages of the reduction. Therefor, the explanation for the experimental results was confined to the tentative and qualitative suggestion.