Nano-indentation behavior of equiatomic Fe–Ni Invar alloy single crystals

The influence of crystallographic orientation on the mechanical behavior of equiatomic Fe–Ni single crystal is examined through nanoindentation. Single crystals were grown using vertical Bridgman technique. Single crystal samples with different orientations were cut from this crystal and the desired faces were polished down to smoothness levels of less than 3 nm. Nanoindentation experiments were carried out on single crystal FeNi alloy samples with [100], [110], and [111] orientations, with peak forces ranging from 500 to 10 000 μN. Hardness values obtained at the highest peak load of 10 000 μN were 2.03 ± 0.02, 2.47 ± 0.04, and 1.97 ± 0.03 GPa for the (100), (110), and (111) faces, respectively. The reduced modulus obtained for peak load of 10 000 μN were 177.91 ± 1.67, 161.69 ± 1.88, and 189.47 ± 1.73 GPa for the (100), (110), and (111) faces, respectively.