Cu-Ni-Feスピノーダル合金におけるセルラー析出

抄録

In connection with spinodal decomposition, the nucleation and growth of cells formed by grain boundary reaction during aging at 673 and 773 K were investigated in Cu-34 mass%Ni-14 mass%Fe and Cu-44 mass%Ni-18 mass%Fe alloys by means of optical and transmission electron microscopy. The results obtained are as follows. Nucleation and growth of grain boundary cell occur remarkably in the later stage of spinodal decomposition in which the wavelength of the modulated structure is unchanged, the amplitude of compositional fluctuation increases and the sine wave of concentration profile of solute atom changes to the square one. In the initial stage of cell formation, the average spacing between the fibrous precipitates is roughly double the wavelength than the wavelength (about 5 nm) of the modulated structure. Nucleation and growth rates of the cells become negligibly small in the later stage of aging in which the coasening reaction of the modulated structure progresses remakably. The driving force for cell nucleation and growth is mainly the difference of total interfacial energy between the fibrous precipitates within cells and the compositional fluctuation or zones in the modulated structure. The activation energy obtained for the cell formation (about 95 kJ/mol) is much smaller than that for the coasening reaction of the modulated structure in these alloys (about 180 kJ/mol). We proposed a model for the cell formation mechanism in these alloys.