MELTING AND SOLIDIFICATION OF SMALL INDIUM PARTICLES EMBEDDED IN AN ALUMINUM-MATRIX

Rutherford backscattering analysis in combination with channeling has been used to study melting and solidification temperature cycles of na nometer-sized indium particles in aluminum. The indium particles were formed by implantation of 100-250 keV In+ atoms into (110) aluminum si ngle crystals using fluences between 1.7 x 10(20) m(-2) and 1.5 x 10(2 1) m(-2). It was found that the smaller embedded indium particles in s ample A (radius 4 nm on average) exhibit higher melting temperature th an the larger inclusions of sample B (radius 40 nm on average). The so lidification of the indium inclusions in sample A also shows larger un dercooling than those of sample B. The superheating of the inclusions of sample A was found to be 23 K and the undercooling was 21 K. These results are in qualitative agreement with earlier TEM results and with simple thermodynamic considerations. By the use of channeling, it was found that a crystal axis of the inclusions with a characteristic hal f-width at half maximum value, equal to the fee indium [110] axis, was in perfect alignment with the [110] direction of the aluminum matrix. This indicates a topotactical orientation between the indium inclusio ns and the aluminum matrix. It was expected that the normalized minimu m yield obtained from channeling in the indium inclusions would decrea se with increasing inclusion size, but the opposite was observed. This may indicate an increasing elastic strain in the inclusions with incr easing particle size.