INVESTIGATION OF DEFORMATION PROCESSES IN ARMCO IRON BY MEANS OF INTERNAL FRICTION AT MEGACYCLE FREQUENCIES

Abstract

Internal friction, employing frequencies in the megacycle range, has been used in order to study the characteristics of elastic and plastic deformation in Armco iron. Tensile stresses only were applied in the present investigation.Among the characteristic features observed three were investigated in detail. (1) A decrease in ultrasonic attenuation at external static stresses within the elastic range, which appears to be related to the ordering effect of the stress on magnetic domains, was investigated. (2) An initial increase in attenuation values regularly observed in cold-worked specimens upon the application of an external load was shown to be associated with the internal stresses. (3) The changes in attenuation resulting from plastic deformation were found to be insignificant in some instances and large in others. An explanation employing the magnetic domain theory and dislocation mechanisms is suggested.