Abstract Scope |
Dilute Al-Zr-Sc-Zr-Si alloys strengthened by coherent L12 Al3(Sc,Er,Zr) nanoprecipitates have potential applications at temperatures higher than 400 °C. In this work, individual and synergistic effects of micro-addition 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 a combination of techniques such as SEM, TEM, APT, and mechanical testing after various heat treatments. Mn and Mo introduce solid-solution strengthening, contributing to both ambient-temperature strength and elevated-temperature creep resistance. Aging at 400 °C leads to formation of L12 core-shell nanoprecipitates, with Mn partitioning at the core, and Mo partitioning to both the core and precipitate/matrix interface. Mn-modified L12 precipitates exhibit higher number density, while Mo-modified L12 precipitates show improved coarsening resistance. Formation of coarse Al/Si/Mn-rich α-precipitates in the Mn-containing alloy contribute moderate precipitation hardening, but consumes Mn/Si solutes in the matrix, leading to decreased creep resistance of the alloy at overaged conditions. |