Equilibrium concentration of interstitials in aluminum just below the melting temperature

A non-contact EMAT technique of ultrasonic generation and detection was used to make high temperature measurements of the C44 deviation from perfect crystal behavior just below the melting temperature and a much smaller effect for C′, which is to be expected for interstitials in FCC crystals. The results are analyzed to give a detected interstitial concentration of 1.7±0.6×10−4 just below the melting temperature of 933 K. This corresponds to a reasonable range for the interstitial formation enthalpy and entropy, and supports a major prediction of the interstitialcy theory of condensed matter states.