Physico-chemical characterization of nanocrystalline (Fe, Ni) alloys

Nanocrystalline (Fe, Ni) alloys were prepared using pulsed electrodepositio n (PE) and mechanical alloying (MA). When compared with thermally alloyed m etals the phase separation into fee and bcc is more pronounced, but incompl ete mixing cannot be avoided especially in the MA samples. The specific int erfacial enthalpies determined by solution calorimetry (SC) are systematica lly higher than those from differential scanning calorimetry (DSC). Electro motive force (EMF) measurements with solid electrolyte cells showed that th e metastability of fcc alloys (e.g. invar) causes large shifts in the elect rode potential. Corrosion processes' of nanocrystalline (Fe, Ni) were obser ved and studied by atomic force microscopy (AFM), by DSC and especially by electrochemical impedance spectroscopy (EIS). (C) 1999 Acta Metallurgica In c.