Nitrogen Damping Peaks of Iron Alloy Containing Copper

Abstract

Nitrogen damping peaks of alpha-iron containing 1 atomic pct copper were measured with the transverse vibration of about 550 c/s, and with the torsional vibration of about 2 and 5 c/s. Besides the usual nitrogen peak of unalloyed iron, an additional peak was observed on the higher temperature side. Activation energy of the high temperature peak was determined as 19.2 kcal/mol from the peak shift. The origin of the high temperature peak is attributed to the stress-induced diffusion of nitrogen atom in the vicinity of copper atom. The half-width of the high temperature peak is broader than that of a peak having a single relaxation time. The broadening, which was not changed even in the precipitation of copper, is explained by allowing the relaxation time to have an appropriate error-functional distribution. The relation between the peak height and the nitrogen content in solution was disscused. Also the effect of copper on the solubility of nitrogen in solution equilibrated with nitride, Fe₈N, was investigated. It was found that the solubility was increased with the addition of copper.