The high concentration of vacancies induced by β″ phase formation in Al–Mg–Si alloys has been observed by positron annihilation lifetime spectroscopy. These vacancies differ from quenched-in vacancies. The induced vacancies are generated inside or at the interface of the β″ phase, i.e. the β″ phase contains a high concentration of vacancies. The induced vacancies survive during the β″-to-β′ phase transformation. The migration energy of the induced vacancies is determined to be 1.83 ± 0.11 eV, which is about three times higher than that of vacancies in pure Al.
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