Tensile behavior of a nanocrystalline Ni–Fe alloy

The tensile properties, deformation and fracture behavior of an electrodeposited nanocrystalline Ni–15% Fe alloy with an average grain size of 9 nm were investigated. The combination of high strength (2.4 GPa), good tensile elongation (6%) and reasonable fracture toughness (16 MPa m 1/2) obtained for this material suggests that nanocrystalline face-centered cubic metals are inherently ductile and have attractive mechanical properties. The large tensile elongation is proposed to be associated with the persistence of strain hardening at large strains. The results of this study reveal that plastic instability precedes fracture and the degree of reduction in area is much higher under plane stress condition. It is shown that at the nanoscale, consistent with theoretical predictions, the crack follows an intergranular path, but crack propagation is accompanied by considerable plasticity. According to a detailed fractographic analysis, a fracture scenario is established aimed at understanding the tensile fracture process in nanocrystalline face-centered cubic metals.