Effects of Oxidation on the Nanoscale Mechanisms of Crack Formation in Aluminum

Aluminum is an important engineering material used in a variety of applications. Under ambient conditions, a self‐limiting oxide layer forms on the aluminum surface and protects the underlying metal from further oxidation; this oxidation of aluminum affects its mechanical strength. Accordingly, we consider a simple, atomic‐level model of the effect of oxidation on crack formation by examining how cracks form in aluminum and its fully oxidized stable partner α‐Al2O3; the valence electron density plot of the latter is shown in the picture, in which a 1 Å crack has been introduced. We find that the sharp falloff in electron density at Al2O3 surfaces provides a nanoscale explanation for the brittleness of alumina. Structural relaxation diminishes the acceptability of simple interaction models in macroscale simulations and suggests such relaxation should be accounted for in the future.