Synthesis of Cu ₅₀ Co 50- x Ni x alloys by mechanical alloying: effect of severe grain refinement on phase evolution, microstructural features and magnetic properties

Cu50Co50−xNix(x = 2, 5, 10, 20 at. %) ternary alloys were prepared by high-energy ball milling for 40 h to assess the effects of Co substitution by Ni on the structural, thermal and magnetic properties. X-ray diffraction revealed the evolution of single-phase FCC Cu-Co-Ni solid solutions with a broad peak, suggesting a high degree of grain refinement. Line profile analysis by the Williamson-Hall method indicated a reduction in crystallite size and enhancement in lattice strain and dislocation density with increasing milling time. Notable variation in precise lattice parameter, stacking and twin fault probabilities further exhibited evidence of atomic size mismatch effects. DSC showed exothermic peaks associated with structural relaxation, with thermal stability being a function of composition. HRTEM micrographs and corresponding SAED patterns further corroborated the formation of a single-phase FCC structure with uniform nanocrystallinity. VSM analysis revealed a soft ferromagnetic nature in all samples with varying saturation magnetisation and coercivity. The results are promising and point to potential applications of the current alloys as soft magnetic and novel functional materials.