Individual and synergistic effects of Mn and Mo micro-additions on precipitation and strengthening of a dilute Al–Zr-Sc-Er-Si alloy

Dilute Al–Er-Sc-Zr-Si alloys strengthened by coherent Al3(Er,Sc,Zr)(L12) nanoprecipitates have excellent coarsening- and creep-resistance up to 400 °C. Herein, the effects of micro-additions 0.25 at.% Mn and/or 0.10 Mo a dilute Al-0.08Zr-0.014Sc-0.008Er-0.09Si (at.%) alloy are investigated with respect precipitate evolution resulting strengths after different aging treatments. Both provide solid-solution strengthening, contributing ambient-temperature strength, in addition elevated-temperature creep resistance. L12-core-shell created upon at °C exhibit partitioning Sc- Er-rich cores, throughout precipitates. Manganese-modified L12-precipitates higher number density (~7.5 × 1022 m−3 for peak-aged condition), while Mo-modified L12-nanoprecipitates display significantly improved coarsening-resistance. No notable synergistic effect additions strengthening isothermal observed. Isochronal displays, however, that delays formation Al/Si/Mn-rich α-precipitates from 425 475 improve resistance 300 Manganese-bearing more significant effect, as it doubles threshold stress compared Mn-free base alloy. This strong could be result fine (<20 nm) formed during experiments sample. The over-aged Mn-containing samples less resistant due coarsening both existing absence creep.