Thermal stability of electrodeposited nanocrystalline nickel and iron - nickel alloys

摘要

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 deg C resulted in abnormal grain growth with an activation energy of 122+-15 kJ mol~(-1). Abnormal grain growth in Fe - 50 at.- percent Ni was only observed at 400 deg C but not at 220 or 300 deg C, where grain growth was very slow. In Fe - 33 at.- percent Ni, room temperature aging resulted in the formation of large grained areas (approx 1 #mu#m), some of which transformed to bcc. In heat treated nickel specimens, some evidence of sulphur and carbon enrichment was found at grain boundaries.