The phase stability of Cu-16 at. % Al and Cu-30 at. % Al alloys obtained by a planetary and an horizontal mills was investigated. The analysis was carried out using X-ray diffraction and various transmission electron microscopy (TEM) techniques. X-ray diffraction analysis gives a statistical overview of the main equilibrium phases present. Meanwhile, the different TEM techniques allow the detection of either the minor phases or the ones having crystalline domains smaller than 5 nm. The solid solution equilibrium a phase was obtained using both milling processes on the Cu-16 at. % Al. Instead, the final intermetallics observed for Cu-30 at. % Al were not the equilibrium ones according to the phase diagram. The planetary mill produced a mixture of a and gamma(2) phases and less than a 2 at. % of beta phase. The horizontal mill produced a gamma(2) phase and less than a 2 at. % of alpha(2) and gamma phases. For both compositions, the horizontal mill seems to be more efficient to achieved the equilibrium intermetallic compound. (C) 2014 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.