In 1932, Mehl, Barrett and Rhines published data on the nature of the precipitates in aluminium alloys containing copper and magnesium silicide respectively. They found in the first case that the precipitation of CuAl
2
from solid solution took the form of plates parallel to the (100) plane in the solid solution lattice. These investigators remarked: “The etching reaction of the particles found was so indefinite, because of the minuteness of the particles, that it' could not be used to identify the phase. Since, however, Schmid and Wassermann have found CuAl
2
in over-aged alloys with 4.5 % Cu, and since in the present work diffraction lines correspond in position to those from CuAl
2
, we may consider the precipitate observed to have been CuAl
2
.. . . These photographs show the precipitate to be chiefly in the form of plates....Furthermore, these plates are well defined in low copper concentrations but poorly defined in high....In figs. 2 and 3 (1 % Cu alloys aged 5 days at 350 and 360° C respectively) there is shown one family of plates lying nearly in the plane of polish, and two others, the edges of which form approximately a right angle, the plates in the plane of polish are especially evident in fig. 3.”
Age hardening and mechanical properties of rapidly solidified Al-9%Zn-2.5%Mg-1%Cu alloys containing transition metals.
