Simplified Experiment Demonstrating Interstitial Diffusion in Alpha Iron

Abstract

An experiment is described which demonstrates the diffusion of interstitial impurities in alpha iron. It consists in the measurement of the logarithmic decrement of the oscillatory motion of a torsional pendulum utilizing a commercially available iron suspension wire of high purity. From the results obtained over a conveniently small temperature range, the activation energy for diffusion of the predominant impurity—nitrogen—can be found. This energy agrees favorably with earlier determinations made over a much wider temperature range using iron wire with specially introduced impurities.