Solid-state alloying in binary systems with a positive heat of mixing

The Extended X-ray Absorption Fine Structure (EXAFS) technique has been employed to monitor the formation of metastable alloys by mechanical alloying in two positive-heat-of-mixing systems, Cu-Fe and Ag-Fe. With its unique atom selectivity and local atomic environment sensitivity, EXAFS provides clear evidence of atomic-level alloying forming bcc (Fe₈₀Cu₂₀) and fcc (Fe₅₀Cu₅₀) solid solutions in the Cu-Fe system. In contrast, such alloying appears to be absent in Ag-Fe. The possible availability of a thermodynamic driving force for alloying in certain nanostructured mixtures of immiscible elements is discussed. A preliminary study was performed on the possibility of alloying and amorphization in vacuum-deposited Cu/Ta multilayer films.