On the effect of matrix relaxation during the melting of embedded indium particles

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Abstract
The melting transformation of micron-sized (1–20 pm in diameter) indium particles embedded in an aluminium matrix has been studied using differential scanning calorimetry. An average elevation in the melting-temperature of 4°C was observed for particles embedded in the grain interiors, whereas particles situated at high-angle boundaries melted at the equilibrium temperature. The relative contributions from interfacial surface energy and strain energies resulting from thermal expansion mismatch and a volume change upon transformation to the melting-temperature were calculated. It was shown that the volume transformation stress upon melting was the major factor in causing the melting-temperature elevation. The difference between the melting behaviour of the embedded and the grain-boundary inclusions was related to differences in the rate of stress relaxation associated with the formation of the liquid nuclei. Volume changes at the grain-boundaries were rapidly accommodated by diffusional processes, whereas the matrix behaved in a rigid manner with respect to particles embedded in the grain interiors.