Non-equilibrium solid solution and nanocrystal structure of Fe–Cu alloy after plastic deformation under pressure

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Abstract
A nanocrystal structure and non-equilibrium solid solution of Fe-20 at.% Cu has been obtained after severe plastic deformation and additional heating. Thin disc samples were pressed at up to 11 GPa between Bridgman anvils and then deformed by rotating one anvil about the other. Cu does not normally form a solid solution with Fe if the Cu concentration exceeds 3 at.%, and only Cu (f.c.c.) and Fe (b.c.c.) lines were revealed by X-ray diffraction from the initial master alloy. After deformation (ϵ = 6.4), broadened Cu and Fe lines were obtained. After further deformation (ϵ = 7.1) only b.c.c. Fe broadened lines were found. On additional heating up to 850–950°C, narrow f.c.c. Cu and b.c.c. Fe lines reappeared. The structure of the samples was investigated by electron microscopy. After deformation to ϵ = 6.4, the sizes of the grains were 10–50 nm and beyond ϵ = 7.1, they were 5–20 nm. According to X-ray and nuclear gamma resonance data, a redistribution of atoms and the formation of a solid solution of Fe-20 at.% Cu took place during deformation. A non-equilibrium solid solution of Fe-20 at.% Cu is also obtained after heating deformed ϵ = 6.4 samples up to 400°C.