Structure and Properties of Nanostructured Vacuum-Deposited Foils of Invar Fe–(35–38 wt%)Ni Alloys

Abstract

The process of electron beam vacuum deposition of the Fe–(35–38 wt%)Ni alloys at substrate temperatures Ts from 300 to700 °C were used to produce vacuum-deposited foils with the FCC structure, differing by the size of characteristic microstructural elements (grains and subgrains). It was shown that refinement of foil microstructural elements to nanoscale is accompanied by their microhardness increase up to 4–5 GPa. The change of the thermal expansion coefficient (TEC) of the nanostructured (NS) foil of the Fe–35.1Ni alloy within the temperature range from −50 to 150 °C has some deviation from that observed for cast Invar alloy of the same composition. It has been found that the main factors affecting the peculiarities of thermal expansion of the NS foil can be related to the presence of small fraction of BCC-phase in them, high level of crystalline lattice microstrains and inhomogeneous magnetic order in FCC-phase. It was shown that as a result of additional thermal treatment of NS foils their invar properties become similar to that observed for cast Invar alloy but mechanical properties remain on the same level.