Abstract
The morphological changes in a modulated structure in Ni-38 at%Cu-5 at%Si alloy during aging were investigated by means of electron microscopy and electrical resistivity measurement.
The satellites associated with the main reflection spots in the electron diffraction were found to be useful for determining the wavelengths of composition modulation produced in the early stage of spinodal decomposition. In the early stage of aging the wavelength of the modulated structure retained a constant value depending on the aging temperature, and then it increased gradually with aging time. It was found that the resistivity of the alloy initially decreased slightly but steadily with aging and turned to a marked increase with further aging.
The spinodal temperature of the alloy was determined to be 645°C from a theoretically predicted linear relationship between a square of the wavenumber of composition modulation and aging temperature. The temperature was in good agreement with the results of electron micrography and resistivity measurement.
