Mechanical alloying of immiscible elements: Experimental results on Ag‒Cu and Co‒Cu

Abstract

Equimolar solid solutions of Ag‒Cu and Co‒Cu were prepared by mechanical milling of the elements. The structure and the thermodynamic properties of the resulting phases were analysed by X-ray diffraction, scanning electron microscopy and differential scanning calorimetry. Large mixing enthalpies (ΔH = 6–8kJg-atom⁻¹ and ΔH = 4–8kJg-atom⁻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 of grain refinement down to the nanometre scale and is assisted by an atomic-scale dissolution. The possible role played by coherent interfaces in substantially increasing the energy of the solid solutions is discussed.