MELTING AND SOLIDIFICATION OF BISMUTH INCLUSIONS IN ALUMINUM

Supercooling of crystalline bismuth inclusions in aluminium crystals h as been observed and studied with different techniques: x-ray diffract ion, in situ Rutherford backscattering/channelling spectrometry and tr ansmission electron microscopy. The results of the measurements with d ifferent experimental methods (and on different samples) agree remarka bly well. The inclusions melt at temperatures at or below the bismuth bulk melting point, and the solid/liquid phase transition exhibits a h ysteresis of 100-150 K. Average inclusion sizes ranged from a few nm t o some tens of nm. The x-ray diffraction melting data are discussed in relation to different existing models for the melting temperature of an inclusion as a function of its size. From this an approximate size distribution for the inclusions is derived.