Structural and compositional study of precipitates in under-aged Cu-added Al-Mg-Si alloy

Takuya Maeda, Kenji Kaneko, Takuya Namba, Yuki Koshino, Yukio Sato, Ryo Teranishi, Yasuhiro Aruga

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    Abstract

    Atomic scale characterization of fine precipitates in an under-aged Cu added Al-Mg-Si alloy was carried out by combination of atomically-resolved annular dark-field scanning transmission electron microscopy and energy dispersive X-ray spectroscopy. Two types of precipitates were observed in the alloy. In the case of ordered β” precipitates, β” was proposed as Mg5-xAl2+xSi4 (x ≈ 1) with solute Cu atoms replacing Al site of β” precipitate. In the case of disordered precipitates, the precipitates were found to consist of β” sub-unit cells, three-fold symmetric structure without Cu atoms, Cu containing structures termed as “Cu sub-unit cluster”, and Q’ sub-unit cells. Among these structures, the morphologies of three-fold symmetric structure without Cu atoms, Cu sub-unit cluster, and Q’ sub-unit cell were almost the same, so that these structures should be the clusters of Q’ phase. Since the areal density, length and diameter of precipitates were almost equal between Cu free Al-Mg-Si alloy and Cu added Al-Mg-Si alloy, the increase of hardness by Cu addition should be due to the precipitation of Cu related precipitates, such as Cu sub-unit clusters and Q’ sub-unit cells.

    Original languageEnglish
    Article number16629
    JournalScientific reports
    Volume8
    Issue number1
    DOIs
    Publication statusPublished - Dec 1 2018

    All Science Journal Classification (ASJC) codes

    • General

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