Characterization of precipitate evolution in an artificially aged Al-Zn-Mg-Sc-Zr alloy

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

卷:527

Article

Wu, Ling-Mei²  Seyring, Martin¹  Rettenmayr, Markus¹  Wang, Wen-Hsiung² 

[1] Univ Jena, Dept Met Mat, D-07743 Jena, Germany

[2] Natl Taiwan Univ, Dept Mech Engn, Taipei 106, Taiwan

关键词: Al-Zn-Mg-Sc-Zr alloy;    Age hardening;    Precipitation;    Transmission electron microscopy (TEM);   

DOI  :  10.1016/j.msea.2009.09.023

来源: Elsevier

【 摘 要 】

The precipitates of an age-hardenable Al-Zn-Mg-Sc-Zr alloy aged at 140 degrees C have been studied by transmission electron microscopy (TEM). The results are interpreted in terms of structural transformations that involve two types of Guinier-Preston (GP) zones (I and II), the metastable eta' hardening precipitate and the stable phase eta-phase (MgZn2). At early stages of ageing, the GPI zones act as nucleation sites for the plate-like eta' phase which precipitates on the {1 1 1}(Al) plane. The transformation from eta' to eta occurs gradually at longer ageing times. The eta particles mainly consist of eta(1) and eta(2) phase, with small amounts of eta(4) type and minor quantities of eta' type structures. Furthermore, while a fine dispersion of coherent Al-3(SC,Zr) precipitates is known to have a beneficial effect on the strengthening of the alloy, the formation of GPII zones is suppressed in the presence of zirconium that leads to a reduction in the amount of eta' formed during subsequent ageing. (C) 2009 Elsevier B.V. All rights reserved.

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