Temperature-dependent mechanical behavior of a nanostructured Ni–Fe alloy

The effect of temperature on mechanical behavior of a nanocrystalline Ni–20% Fe alloy with a grain size of 22 nm was studied in the temperature range of 4.2–300 K. The results show that this nanocrystalline alloy possesses both high strength and large plastic strain at 300 and 77 K. Moreover, the mechanical performance at 77 K is better than that at 300 K. However, the plastic strain decreases notably and the stress–strain curves become serrated at 4.2 K. In addition, it is found that the strain rate sensitivity decreases with decreasing the temperature, and the strength softening happens at high strain rates at 77 K. Finally, the results demonstrate that the strain hardening ability decreases at 77 K and vanishes at 4.2 K for small grain sizes.