Coarsening resistance at 400 °C of precipitation-strengthened Al–Zr–Sc–Er alloys
| Autor: | David N. Seidman, Christopher Booth-Morrison, David C. Dunand |
|---|---|
| Rok vydání: | 2011 |
| Předmět: |
Zirconium
Materials science Nanostructure Polymers and Plastics Precipitation (chemistry) Metallurgy Alloy Metals and Alloys Nucleation chemistry.chemical_element engineering.material Indentation hardness Electronic Optical and Magnetic Materials chemistry Chemical engineering Aluminium Ceramics and Composites engineering Scandium |
| Zdroj: | Acta Materialia. 59:7029-7042 |
| ISSN: | 1359-6454 |
| Popis: | The effect of substituting 0.01 or 0.02 at.% Er for Sc in an Al–0.06 Zr–0.06 Sc at.% alloy was studied to develop cost-effective high-temperature aluminum alloys for aerospace and automotive applications. Spheroidal, coherent, L12-ordered Al3(Sc, Zr, Er) precipitates with a structure consisting of an Er-enriched core surrounded by a Sc-enriched inner shell and a Zr-enriched outer shell (core/double-shell structure) were formed after aging at 400 °C. This core/double-shell structure strengthens the alloy, and renders it coarsening resistant for at least 64 days at 400 °C. This structure is formed due to sequential precipitation of solute elements according to their diffusivities, D, where DEr > DSc > DZr at 400 °C. Zr and Er are effective replacements for Sc, accounting for 33 ± 1% of the total precipitate solute content in an Al–0.06 Zr–0.04 Sc–0.02 Er at.% alloy aged at 400 °C for 64 days. Er accelerates precipitation kinetics at 400 °C, resulting in: (i) strengthening due to the elimination of lobed-cuboidal precipitates in favor of spheroidal precipitates; and (ii) a decrease in the incubation time for nucleation because DEr > DSc. Finally, a two-stage aging treatment (24 h at 300 °C + 8 h at 400 °C) provides peak microhardness due to optimization of the nanostructure. |
| Databáze: | OpenAIRE |
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