Effects of Mn and Mo Micro-additions on Al–Zr–Sc–Er–Si Mechanical Properties

Abstract

Dilute Al–Zr–Sc–Er–Si alloys strengthened by coherent L12 Al3(Sc, Er, Zr) nanoprecipitates have potential applications at temperatures higher than 400 °C. In this research, the effects of micro-additions of 0.25 at.% Mn and/or 0.10 at.% Mo to a dilute Al-0.08Zr-0.014Sc-0.008Er-0.09Si (at.%) alloy were investigated using atom-probe tomography, as well as mechanical testing after different heat treatments. Molybdenum and manganese result in solid-solution strengthening. Aging at 400 °C leads to the formation of core-shell (L12 structure) nanoprecipitates, with Mn partitioning to the core, and Mo partitioning to both the core and nanoprecipitate/matrix interface. Manganese-modified L12 nanoprecipitates exhibit a higher number density, while Molybdenum-modified L12 nanoprecipitates display an improved coarsening resistance.