Determination of the phase composition of the intermediate and final products of the synthesis of Cu–Al cermets by a differential dissolution stoichiographic method

Resumo

Intermediate and final products of the synthesis of Cu–Al cermets have been studied by a differential dissolution (DD) stoichiographic method. Their qualitative and quantitative phase compositions have been determined. The phase composition of the intermediate products has been shown to differ from that of the final products. It has been shown that the first stage of the synthesis is the formation of a solid solution and intermetallic phase. In the final stage, the latter decomposes to give a solid solution, copper, and aluminum. The degree of decomposition depends on the mechanical activation time of the constituent metals: milling for 12 min leads to complete decomposition of the intermetallic phase. We also observe the oxidation of the forming aluminum and copper to their oxides and partial interaction between them, resulting in the formation of solid solutions of aluminum oxide in copper oxide. A comparative analysis of DD data with results obtained by physical methods— X-ray diffraction (XRD) and nuclear magnetic resonance (NMR)—demonstrates that they do not always agree. The reason for such discrepancies is that the three methods have different capabilities. We thus conclude that the use of both DD and XRD is crucial for obtaining reliable results.