The relationships between structure and properties of irradiated materials is an important focus of radiation damage studies. A knowledge of these relationships can enable us to tailor the properties of materials to enhance their radiation resistance. Magnesium aluminate spinel is an obvious choice for such a study, because it is known to resist radiation damage when irradiated with fast neutrons or energetic ions. Recent work has shown, for the first time, that MgAl2O4 can be amorphized at cryogenic temperatures following ion irradiation. Electron diffraction patterns, obtained after irradiating spinel with 400 keV Xe2+ at 100 K to various doses upto 25 dpa, show that the first-order reflections decrease in intensity and become extinct with increasing dose. If the dose is increased further, the material becomes amorphous. We have performed a systematic study of this phase transformation by obtaining the diffraction patterns, and measuring the Young's modulus and nanohardness of the irradiated layer.