Exploring the relative influence of atomic parameters on solid solution strengthening

Developing predictive models for solid solution strengthening is a key tool in alloy design, enabling the optimization of mechanical properties. This study aims to identify the primary factor governing solid solution strengthening, providing foundations for more accurate predictive models. In this work single-phase solid solution alloys are developed with differences in atomic volume and electronegativity among constituent elements. Unlike previous studies focusing on only one factor, this work employs alloys specifically designed to assess both variables simultaneously, operating at the boundary conditions of different strengthening models. Vanadium is selected for its large electronegativity difference relative to nickel, while palladium is chosen for its significant atomic volume difference. We demonstrate that atomic volume differences play a dominant role in solid solution strengthening. Moreover, each solid solution exhibits a critical grain size below which grain refinement influences mechanical properties more than solid solution strengthening. Finally, a Ni₅₀Pd₅₀ alloy is produced showing a stability of mechanical properties with increasing grain size. Previous models explain solid-solution strengthening by differences in atomic volume and electronegativity of the constituent atoms. Here, the authors consider both factors simultaneously and identify atomic volume as the dominant factor for FCC alloys.