| Thermal stability of nanostructured (NS) nickel based alloy Inconel 718 has been investigated. This structure was formed by severe plastic deformation (SPD) via high pressure torsion (HPT) and multiple isothermal forging (MIF) of the alloy with an initial coarse-grained (CG) structure. The produced microstructures were analyzed. Such NS conditions are characterized by the nonequilibrium grain boundaries and the high hardness value that is twice larger than that of a CG alloy. Tensile tests of NS alloy after MIF have shown very high room-temperature strength. Thermal stability of the studied structural conditions of the alloy depends on the presence and stability of the precipitates of δ- and γ"-phases, each of which, in accordance with its quantity, sizes, coherence with matrix, prevents the grain growth. |
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