Anisotropic Grain Growth in Iron-Carbon Films at High Electric Current Densities

Abstract

We investigate the effect of direct electric current (DC) on grain growth in 110 nm thick iron-carbon films with carbon concentrations at 2.7 at%. The application of DC-current during annealing at 550°C confirms the expected transport of carbon in the direction of the electric current and the unexpected formation of elongated, abnormally large carbide and ferrite grains along the current direction in the carbon-rich regions. The formation of elongated grains is explained by electromigration-induced carbon flux divergences that result from the carbide precipitates. This presents a possible scenario for controlling microstructure evolution in iron by using DC electric currents.

Keywords: thin films, electromigration processing, abnormal grain growth, iron-carbon, electron microscopy