First-Principles Design of Alloy Systems, Part I: Effects of Solute Type, Concentration, and Distribution on Alloying and Mechanical Properties – As-Quenched Dilute Al (Mg, Si) Alloys

Abstract

Solid solution strengthening is a well-known strengthening mechanism for Al (Mg, Si) alloys. The distribution of solute atoms plays an important role in the enhancement of the mechanical properties. As-quenched, dilute, Al alloys are analysed by atom probe tomography (APT) and mechanical testing (microhardness, tensile testing) and these data have been employed in order to assess the 3D distribution of solute atoms in the solid solutions. An innovative approach is to abstain from the conventional logic of binary versus ternary alloys in data analysis in favor of a less-concentrated versus more-concentrated strategy. This approach enables for the first time that the integration of first-principles Condon–Morse atomic interaction effects, APT, and mechanical testing, and first principles effects (field, proximity, chemical, and atomic size), which results in a novel empirical singleton-cluster plot. The plot allows differentiation between singletons, solute clusters, and coclusters as well as between the less-concentrated and more-concentrated alloys. The plot also allows determination of the maximal yield strengths from cluster strengthening and from singletons in the absence of clustering. Most critically, this new approach in data analysis allows for the first time the determination of the dmax (maximal distance between solutes in a cluster) based on experimental results.