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

MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING

卷:800

Article

Shu, Shipeng¹  De Luca, Anthony^1,2  Dunand, David C.¹  Seidman, David N.^1,3 

[1] Northwestern Univ, Dept Mat Sci & Engn, 2220 Campus Dr, Evanston, IL 60208 USA

[2] Empa, Swiss Fed Labs Mat Sci & Technol, Lab Adv Mat Proc, Uberlandstr 129, CH-8600 Dubendorf, Switzerland

[3] Northwestern Univ, Ctr Atom Probe Tomog, 2220 Campus Dr, Evanston, IL 60208 USA

关键词: Aluminum alloys;    Precipitation-strengthening;    Creep;    Atom-probe tomography;    Transmission electron microscopy;   

DOI  :  10.1016/j.msea.2020.140288

来源: Elsevier

【 摘 要 】

Dilute Al-Er-Sc-Zr-Si alloys strengthened by coherent Al3(Er,Sc,Zr)(L12) nanoprecipitates have excellent coars eningand creep-resistance up to 400 degrees C. Herein, 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 are investigated with respect to precipitate evolution and the resulting strengths after different aging treatments. Both Mn and Mo provide solid-solution strengthening, contributing to ambient-temperature strength, in addition to elevated-temperature creep resistance. L12-core-shell nanoprecipitates created upon aging at 400 degrees C exhibit Mn partitioning at the Scand Er-rich precipitate cores, and Mo throughout the precipitates. Manganese-modified L12-precipitates exhibit a higher number density (-7.5 x 1022 m3 for peak-aged condition), while Mo-modified L12-nanoprecipitates display significantly improved coarsening-resistance. No notable synergistic effect of Mn and Mo additions strengthening upon isothermal aging at 400 degrees C are observed. Isochronal aging displays, however, that a Mo addition delays the formation of Al/Si/Mn-rich alpha-precipitates from 425 degrees C to 475 degrees C. Both Mn and Mo additions improve the creep resistance of the alloys at 300 degrees C. Manganese-bearing alloys exhibit a more significant effect, as it doubles the threshold stress compared to the Mn-free base alloy. This strong effect could be a result of fine alpha-precipitates (<20 nm) formed during the creep experiments at 300 degrees C for the peak-aged sample. The over-aged Mn-containing samples are less creep resistant due to coarsening of both existing L12-nanoprecipitates and the absence of fine alpha-precipitates formed during creep.

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