Melting and crystallization of Xe nanoprecipitates in Al under 1 MeV electron irradiation

Xe nanoprecipitates have been produced by ion implantation into high purity Al at 300 K. With an off-zone axis high resolution imaging technique, Xe nanocrystals may be clearly structure imaged against a weak structure image of the Al matrix. Under the 1 MeV electron irradiation employed for the HREM observation, the nanoprecipitates exhibit a number of readily observed phenomena including migration within the matrix, changes in shape, faulting, melting, crystallization and coalescence, associated with changes in interface structure. This paper examines the possible mechanisms for melting and crystallization of the nanoprecipitates: beam heating and changes in precipitate volume associated with fluctuations in arrival of Al vacancies and interstitials, or with transport of Xe to and from the Al matrix due to electron irradiation damage in the Al and/or the Xe. Biased fluctuations in the point defect fluxes will produce volume changes in the Al cavity confining the Xe with corresponding deviations from the equilibrium pressure, 2γ/R₀, associated with the interfacial tension γ.