Thermal stability of electrodeposited nanocrystalline nickel and iron–nickel alloys

Abstract

The thermal stability of electrodeposited nanocrystalline nickel and iron–nickel alloys has been studied using TEM, X-ray diffraction, and atom probe analysis. All of the as deposited materials were purely fcc and had grain sizes of 10–20 nm. Heat treatment of nanocrystalline nickel in the range 190–320°C resulted in abnormal grain growth with an activation energy of 122±15 kJ mol-1. Abnormal grain growth in Fe–50 at.-%Ni was only observed at 400°C but not at 220 or 300°C, where grain growth was very slow. In Fe–33 at.-%Ni, room temperature aging resulted in the formation of large grained areas (∼1 µm), some of which transformed to bcc. In heat treated nickel specimens, some evidence of sulphur and carbon enrichment was found at grain boundaries.