Effect of microstructure of vacuum-deposited Fe100−xNix (30 < x < 39) foils with FCC structure on their mechanical properties

The present paper considers the relation between microstructure characteristics of vacuum-deposited Fe100−xNix (30 < x < 39) foils and their mechanical properties. The foils 40-100 μm thick with various microstructure characteristics were prepared using electron beam physical vapor deposition (EBPVD) onto substrates maintained at different temperatures in the 250-700 °С range. The foil microhardness increases as deposition temperature decreases and reaches the maximum value of 5 GPa for foils deposited at 300 °C. It has been shown that the crystallite size in the foils decreases monotonically from sub-micron values (over 100 nm) to nanoscaled ones (10-20 nm), while the level of microstrains of FCC lattice increases to 1% with lowering deposition temperature. The dependence of foil microhardness on the crystallite size in the Hall-Petch's coordinates (Hμ vs d−1/2) exhibits the deviation from a linear function at microhardness of 5 GPa. Such behavior of the foil microhardness at decreasing deposition temperature correlates with an abrupt increase in both porosity and microstrains level.