Abstract
The internal friction in a quench-hardened plain carbon steel containing 0.12% of carbon and a cold-worked iron containing 0.019% of carbon was measured by means of a torsion pendulum with a frequency of vibration of about 1.7 cycles per second. Three anelastic effects were observed in each material. The anelastic effects observed in the quench-hardened steel correspond to those observed in the cold-worked iron respectively. These are observed as distinct relaxation peaks at about 40°C and 230°C and a continuous increase in internal friction with a rise of measuring temperature from about 280°C. The 40°C-peak is attributed to the stress-induced ordering of interstitial solute atoms and disappears as a result of the aggregation of interstitial solute atoms around dislocations after tempering at a low temperature. The presence of a so-called Snoek peak in the as-quenched steel is due to an unavoidable tempering during quenching. The temperature, the activation energy and the width at half-maximum height for the 230°C-peak in the quench-hardened steel are the same as those in the cold-worked iron. The 230°C-peak is considered to be due to the stress-induced movement of dislocations subjected to a viscous drag by Cottrell atmospheres. The continuous increase in internal friction with the rise of measuring temperature at the higher temperature range seem to be caused by the coupled relaxations of an irregular network of sub-grain interfaces. The structure of martensitic matrix in quench-hardened low carbon steel is similar to that of a cold-worked iron.
