GP-zones in Al-Zn-Mg alloys and their role in artificial aging

• The structure of GP-zones in an industrial, 7xxx-series Al–Zn–Mg alloy has been investigated by transmission electron microscopy methods: selected area diffraction, conventional and high-resolution imaging. Two types of GP-zones, GP(I) and (II) are characterized by their electron diffraction patterns. GP(I)-zones are formed over a wide temperature range, from room temperature to 140–150°C, independently of quenching temperature. The GP(I)-zones are coherent with the aluminum matrix, with internal ordering of Zn and Al/Mg on the matrix lattice, suggested to be based on AuCu(I)-type sub-unit, and anti-phase boundaries. GP(II) are formed after quenching from temperatures above 450°C, by aging at temperatures above 70°C. The GP(II)-zones are described as zinc-rich layers on {111}-planes, with internal order in the form of elongated domains. The structural relation to the η′-precipitate is discussed.

Ämnesord

NATURVETENSKAP  -- Fysik -- Den kondenserade materiens fysik (hsv//swe)

NATURAL SCIENCES  -- Physical Sciences -- Condensed Matter Physics (hsv//eng)

NATURVETENSKAP  -- Kemi -- Oorganisk kemi (hsv//swe)

NATURAL SCIENCES  -- Chemical Sciences -- Inorganic Chemistry (hsv//eng)

Nyckelord

aluminum alloys

transmission electron microscopy (TEM)

electron diffraction

nucleation growth

Guinier-Preston zones

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