Abstract
High angle annular dark field scanning transmission electron
microscopy has been employed to observe precipitate
structures in Al–Zn–Mg and Mg–Zn alloys. h1 precipitate
structures in Al–Zn–Mg are commonly formed by MgZn2
Penrose bricks, but also frequently observed to incorporate
Mg6Zn7 elongated hexagons via two different modes.
Tilings of MgZn2 and Mg6Zn7 building blocks in both Beta′
1 inMg–Zn and eta1 in Al–Zn–Mg alloys, create overall patterns
which deviate from the chemical and structural
configuration of solely monoclinic Mg4Zn7 or MgZn2 unit
cells. Precipitate morphologies were found to be correlated
to their internal sub-unit cell arrangements, especially to
Mg6Zn7 elongated hexagons. Systematic or random
arrangements of Mg6Zn7 elongated hexagons inside
precipitates and therefore compositional and structural
patterns, were found to be strongly related to the aspect
ratio of the precipitates and altering of the precipitate/
matrix interfaces
microscopy has been employed to observe precipitate
structures in Al–Zn–Mg and Mg–Zn alloys. h1 precipitate
structures in Al–Zn–Mg are commonly formed by MgZn2
Penrose bricks, but also frequently observed to incorporate
Mg6Zn7 elongated hexagons via two different modes.
Tilings of MgZn2 and Mg6Zn7 building blocks in both Beta′
1 inMg–Zn and eta1 in Al–Zn–Mg alloys, create overall patterns
which deviate from the chemical and structural
configuration of solely monoclinic Mg4Zn7 or MgZn2 unit
cells. Precipitate morphologies were found to be correlated
to their internal sub-unit cell arrangements, especially to
Mg6Zn7 elongated hexagons. Systematic or random
arrangements of Mg6Zn7 elongated hexagons inside
precipitates and therefore compositional and structural
patterns, were found to be strongly related to the aspect
ratio of the precipitates and altering of the precipitate/
matrix interfaces