The microstructure changes of aluminum under implantation with Ni+ ions were investigated. The ion implantation was carried out at 250 keV Needle-like precipitates were formed in the Al matrix after implantation to 0.2 x 10(17) Ni+ cm(-2). This precipitate contained between 8.5 and 13.3 at.% Ni. The growth of the precipitates was connected with an amorphous phase under further implantation up to 2 x 10(17) Ni+ cm(-2). The concentration of Ni in the, amorphous phase was 10.8-12.8 at.%. In order to investigate the phase stability of the precipitate, annealing or electron irradiation experiments were performed in a high voltage electron microscope. The crystalline and the amorphous phases were stable under electron irradiation up to 5 dpa. The crystalline phases were also stable during annealing at 673 K, whereas the amorphous phase was crystallized during annealing at 593 K. (C) 2003 Elsevier Science B.V. All rights reserved.