Metastable phase formation and activity estimation of the Ag-Cu system prepared by mechanical alloying

Mechanical alloying (MA) process produces a series of supersaturated solid solutions (s.s.) in the silver-copper system. Metastable solutions produced are with nanometer scale grains and consists of severely distorted structures, having a high content of stored energy, therefore the effective activities of the elemental powders increase as the ball milling process goes on. The measured activity values, by means of the electromotive force (emf) technique shows unusual great departures from the Raoult's law. In spite of silver nobility the huge activity values, exhibited by the MA samples resulted in a quick oxidation reaction, when anodically polarizing the metastable surfaces in an acidic testing solution. A better corrosion resistance behaviour is recognized for the s.s. alloys produced by the high energy ball milling than those conventionally produced by the rotational low energy ball milling process.