Effect of Annealing on the Room-Temperature Internal Friction of 65 per cent Reduced Commercially Pure Aluminium

Abstract

The purpose of this paper is to report on a study of the effect of annealing processes on the room-temperature internal friction of cold-worked commercially pure aluminium. Since we considered that the measurements of the room-temperature internal friction after repeated higher temperature annealing might be a useful tool for the study of the mechanisms of annealing processes in terms of elementary atomic processes. We have carried out the present study. The effect of the temperature of repeated annealing, say, 13° to 600°C, upon the room-temperature internal friction of 65.4% reduced commercial aluminium was observed by the transverse vibration of about 2,000 c.p.s. From the present results it was revealed that in general trend the internal friction changed along the room-temperature annealing versus the annealing-temperature curves consisting of the first descending part attributable to the segregating process by which the impurity atoms segregate round the first dislocation line by the stress-induced diffusion in about the 13° to 120°C range, the first rising part attributable to the recovery process in about the 120° to 150°C range,the second rising part attributable to the composite process of a primary nucleation followed by polygonization in about the 150° to 270°C range, the second descending part attributable to the homogeneous coarsening process in about the 270° to 500°C range, and the third rising part attributable to an unknown process in which the behavior could not be clearly determined in this experiment, in the range 500°C or higher.