Stressed Aluminium

Abstract

IN the course of an investigation on the behaviour of aluminium (purity 99·998 per cent) after the release of compressional stress to which it had been subjected, it was found that immediately after compression, the lattice parameter was increased, but that in course of time it decreased according to an exponential law, finally reaching a value at room temperature which was higher than the equilibrium value. The rate of recovery increased as the amount of cold work, measured by the percentage reduction in thickness, increased ; but the final constant value reached was the same for all the compressions investigated. On annealing the material for a suitable period after it had reached the ‘metastable' state, the lattice parameter decreased from the metastable to the true equilibrium value.