The Room-Temperature Internal Friction in Iron and Steel—Cold Worked Iron and Steel

Abstract

The room-temperature internal friction in an electrolytic iron, a magnetic soft iron and several commercial low-carbon steels, which were extended by 1∼10%, was measured by the transverse vibration method as described in the previous paper. According to the results obtained immediately after the cold-working, the amplitude-independent internal friction was increased and the amplitude-dependent internal friction was decreased by cold-working as compared to those of the annealed specimens. When the cold-worked specimens were kept at room-temperature, the amplitude-independent internal friction was reduced to a value that was nearly equal to the background damping in the annealed specimens, and the amplitude-dependent internal friction was decreased by a very small but clearly observable amount. The higher the degree of extension was, the more marked were the changes observed in both parts of the internal friction. The principal cause of the amplitude-independent internal friction in cold-worked iron and steel can be considered as representing the loss produced by the reversible movement of dislocation segments which are free from pinning by solute atoms. The reduction in the amplitude-independent and the amplitude-dependent parts during room-temperature aging may be explained by the interaction between the solute atoms and the dislocations, although the reduction of the latter can be observed only for the first few hours in the recovery curve.Some remaining internal friction was observed in specimens that were completely recovered, and the amplitude-independent part seemed to be mostly the tail of the Snoek peak, while the amplitude-dependent part seemed to be the loss due to the magneto-mechanical hysteresis.