This paper discusses the evolution of argon bubbles in an aluminum-40 at% manganese alloy during 50-keV Ar⁺ ion implantation. At low irradiation doses, the argon atoms cluster into platelets as revealed by the intense “streaking” observed in the electron diffraction pattern. At higher doses the extent of streaking reduces and finally disappears when well-resolved argon bubbles form, suggesting the growth of the platelets during irradiation and their ultimate transformation to spherical bubbles.