Effect of Room Temperature Aging Upon the Internal Friction Versus the Cold-worked Levels Relationship of Commercially Pure Polycrystalline Aluminium

Abstract

This paper presents the results of investigations of the effect of room temperature annealing upon the internal friction introduced by cold-working versus the cold-working levels relationship of commercially pure aluminium, by means of transverse vibration about 2000 c.p.s. of squars rods. The internal friction versus the cold-working levels curve for the specimens, annealed for about 30 minutes at room temperature, (11°±2°C), before measurement, produced anomalous peaks at around 15 and 55 pct. reductions, respectively. Although the internal friction introduced by cold-working was diminished with annealing time over the entire range of reduction area, the diminution of internal friction was markedly different by the cold-working levels. The first high peak swaged down with annealing time at room temperature and was decayed completely after an annealing for 2\frac12 days at room temperature. The second small peak was not decayed by a room temperature annealing for 41 days. The removal of the internal friction introduced by cold-working for the 15 pct. reduction area followed the (time)^2⁄3 law, but in the other specimens it did not followed the (time)^2⁄3 law. These observed results were qualitatively discussed.