Stable ductility of an electrodeposited nanocrystalline Ni–20 wt.%Fe alloy in tensile plastic deformation

Abstract

Tensile behavior of an electrodeposited nanocrystalline Ni–20wt.%Fe (average grain size d=∼32nm) alloy was investigated. With the variety of strain rate, high ultimate strength (1762–1939MPa) and stable fracture ductility (8.5–9.3%) were observed during tensile tests. The ductility of the nanocrystalline Ni–20wt.%Fe alloy is more stable than that of the nanocrystalline Ni (5.6–11.3%) with similar microstructures. The stable ductility of the nanocrystalline Ni–20wt.%Fe alloy can be attributed to its higher work hardening ability. Transmission electron microscope analysis revealed that there are massive dislocations, deformation twins and stacking faults in the deformed nanocrystalline Ni–20wt.%Fe alloy. The decrease of stacking fault energy, caused by alloying of Fe element, should be responsible for the crystal defect microstructures and this increases work hardening rate, which can improve the ductility at last.