Thermodynamic analysis and characterisation of nanostructured Cu(Mo) compounds prepared by mechanical alloying and subsequent sintering

The extension of Mo solid solubility in Cu during mechanical alloying was investigated based on thermodynamic modelling and Hume-Rothery rules. To evaluate the theoretical results, experimental studies were launched to produce nanostructured solid solution of Cu(Mo) with different weight percentages of Mo by mechanical alloying, and finally, the products were characterised by X-ray diffraction, microhardness measurements and nanoindentation. Results of the thermodynamic analysis showed that the Gibbs free energy change for the formation of amorphous and crystalline phases in the Cu-Mo system is positive, which means that thermodynamic barriers exist for the formation of solid solution. However, experimental results showed that Cu(Mo) solid solution with the maximum value of Mo solubility of 9.5 wt-% Mo can be produced by mechanical alloying. This extension of Mo solid solubility led to such better mechanical properties because the hardness and elastic modulus of the bulk specimen of Cu-15 wt-% Mo compound were found to be 200 HV and 91.17 GPa respectively.