MECHANICAL ALLOYING OF IMMISCIBLE ELEMENTS - EXPERIMENTAL RESULTS ON AG-CU AND CO-CU

Equimolar solid solutions of Ag-Cu and Co-Cu were prepared by mechanic al milling of the elements. The structure and the thermodynamic proper ties of the resulting phases were analysed by X-ray diffraction, scann ing electron microscopy and differential scanning calorimetry. Large m ixing enthalpies (Delta H = 6.8 kJ g-atom(-1) and Delta H = 4.8 kJ g-a tom(-1) for Ag-Cu and Co-Cu respectively) were measured in the alloyed phases. It is clear that the solid solution forms through a process o f grain refinement down to the nanometre scale and is assisted by an a tomic-scale dissolution. The possible role played by coherent interfac es in substantially increasing the energy of the solid solutions is di scussed.