Microstructural and Compositional Evolution of Ni-Cu Solid Solution versus Mechanical Alloying Speed during Surface Mechanical Coating (SMC)

Recently, surface coating process by mechanical alloying method was considered as a new and fundamental method. The method in this paper was introduced as "surface mechanical coating (SMC)". In this research, effect of speed milling parameters on mechanical surface coating process in the range of 200 to 500 rpm for both 20 and 60 hour milling time was considered. Since the milling speed leads to increased energy and higher chamber temperature, then microstructural and compositional changes in the powder and coating are inevitable. X-ray diffraction, electron probe micro analyzer and scanning electron microscope were used to study the structure and composition properties. It should be mentioned that in this research copper powder and nickel ball were used as initial materials. The results showed that the completed formation of Cu-Ni solid solution was acquired after 20 hours of milling at 400 rpm and 60 hours of milling at 300 rpm. It was found that the thickest coating layer of about 220 µm was obtained after 60 hours of milling at 400 rpm. The solid solution formation mechanism during SMC process was extracted according to microscopic examination.