High substitutional fractions,fs, with values up to 0.87 were measured for Au implanted into Al single crystals at 77 K with peak concentrations up to 5 at.%. This solubility limit exceeds that observed for 293 K implants by one order of magnitude. At higher Au concentrations a transformation takes place most probably into an amorphous phase. Annealing the 77K implants at 293 K leads to a decrease infs. Postirradiation experiments with 300 KeV He and Ar ions at 77 K suggest that the decrease offsupon annealing is maily due to Au precipitate formation.