PHASE TRANSFORMATIONS AND CHEMICAL REACTIONS IN MECHANICALLY ALLOYED CU-ZN POWDERS

The ability of plastic deformation, performed under suitable conditions, to induce solid-state reactions in metallic systems at near room temperature was established several years ago. Following these early experiments it has been repeatedly shown that mechanical alloying (MA) is a very efficient way of achieving true alloying of metallic powders and that, depending on the system under examination and on the process parameters, either equilibrium or metastable phases can be synthesized. It has been established that mechanical milling (MM) of equilibrium intermetallic compounds can lead either to a single metastable phase or to a mixture of phases. Two previous studies on the Cu-Zn system, one performed by MA at near equiatomic composition and the other carried out by cold-rolling of elemental foils in the composition range 25-82 at.% Zn, have conclusively shown the achievement of true alloying in this system. However, a comparison of the two experiments for samples of the same composition shows that the two techniques lead to different end products. Considering that MA experiments have been performed in argon, while cold-rolling has been performed in air, the authors have decided to extend to other compositions the comparison between the two techniques. To this purpose the authors havemore » studied the phase transformation occurring during MA of Cu-Zn powders containing 85 and 80 at. %Zn in presence of air.« less