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 nanometer-sized indium particles in aluminum. The indium particles were formed by implantation of 100-250 keV In+ atoms into (110) aluminum single crystals using fluences between 1.7 x 10(20) m(-2) and 1.5 x 10(21) m(-2). It was found that the smaller embedded indium particles in sample A (radius 4 nm on average) exhibit higher melting temperature than the larger inclusions of sample B (radius 40 nm on average). The solidification of the indium inclusions in sample A also shows larger undercooling 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 half-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 inclusions and the aluminum matrix. It was expected that the normalized minimum yield obtained from channeling in the indium inclusions would decrease with increasing inclusion size, but the opposite was observed. This may indicate an increasing elastic strain in the inclusions with increasing particle size.