An electron work function based mechanism for solid solution hardening

Solid solution hardening is one of common methods to increase hardness of metals by adding solute atoms. The mechanism for solution hardening is ascribed to the differences in atomic size and elastic modulus between the host and the solute. However, the theory is somehow ambiguous without clear clues for optimizing the balance between the two effects towards maximized hardening effectiveness. Current selection of alloying elements for solution hardening is largely based on experience. In this study, we re-examine the conventional mechanism and propose a single-parameter model using electron work function (EWF) as an indicator to evaluate the capability of solute atoms in solid solution hardening. With relevant experiments, we demonstrate the correlation between electron work function and solution hardening effectiveness. The prediction from the proposed EWF model is consistent with the experimental observations.