MATERIALS TRANSACTIONS
Online ISSN : 1347-5320
Print ISSN : 1345-9678
ISSN-L : 1345-9678
Effect of Copper Addition on Precipitation Behavior near Grain Boundary in Al–Zn–Mg Alloy
Kenji MatsudaToru YasumotoArtenis BendoTaiki TsuchiyaSeungwon LeeKatsuhiko NishimuraNorio NunomuraCalin D. MarioaraAdrian LevikRandi HolmestadHiroyuki TodaMasatake YamaguchiKen-ichi IkedaTomoyuki HommaSusumu Ikeno
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2019 年 60 巻 8 号 p. 1688-1696

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The effect of Cu-addition on age-hardening and precipitation have been investigated by hardness measurement, tensile test, high resolution transmission electron microscopy (HRTEM) and high angle annular dark field scanning transmission electron microscopy (HAADF-STEM) techniques. Higher hardness, strength, and lower elongation were caused by increasing amount of Zn + Mg because of increased number density of precipitates. Cu addition also provided even higher peak hardness, strength, and lower elongation. The alloy containing highest Cu content had fine precipitates of GPB-II zones or the second clusters, in the precipitate free zones (PFZs) and the matrix, together with η′/η in the matrix from the early stage of aging. Two regions have been confirmed as the PFZs in the peak aged alloy containing highest Cu: (i) nearest to grain boundary (GB) about 70 nm in width (n-PFZ) and (ii) conventional PFZ about 400 nm in width which can be confirmed by conventional TEM (con-PFZ). The con-PFZ contains fine precipitates consisting of GPB-II zones or the second clusters, even for 2 minutes of aging at 473 K which were not present in the n-PFZ. The fine precipitates, GPB-II zones or the second clusters in the con-PFZ and the matrix disappeared at overaged condition.

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© 2019 The Japan Institute of Light Metals
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