The change in resistivity during extension at 77 K was measured on a Cu-4 wt%Ti alloy aged at relatively low temperatures, 150–450°C. The resistivity of each aged specimen increased with straining at 77 K. The resistivity increment for a strain of 5% became maximum for the specimen aged for a certain period of time at each temperature. The aging time giving the maximum increase in resistivity of the specimen,
tmax, tended to be shorter as the aging temperature increased. It was shown that the resistivity increase observed was due largely to the destruction of the composition modulation or the modulated structure present in the aged specimen. It was suggested that the time
tmax indicated a characteristic time
ts at which spinodal decomposition of the alloy was completed and the amplitude of the composition modulation became maximum at a given temperature.
tmax coincided well with
ts which was determined from X-ray small-angle scattering experiments on this alloy. Based on Cahn’s theory of spinodal decomposition, the temperature dependence of
ts was found to be given by the relation:
(
Remark: Graphics omitted.)
where
Ts was the coherent spinodal temperature and
E the activation energy for diffusion of solute atoms in the alloy. With the observed values
ts\simeq
tmax and
Ts\simeq350°C, we obtained
E\simeq0.8 eV . This value was reasonable for the diffusion of Ti atoms in the alloy during the early stages of aging at relatively low temperatures.
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