Measurements of internal friction and Young’s modulus were made by a bending vibration method with a frequency of about 520∼680 Hz in a temperature range from 293 K to 433 K on the Cu-13.8 wt%Al-7.9 wt%Ni alloys obtained at various cooling rates after solution heat-treatment at 1223 K for 1.8×10
3 s, where effects of cooling rates on the temperature behavior and the values of internal friction were discussed.
It was found that the main-peak (
Pm) always appeared at a constant temperature of 323 K in all specimens which were cooled at the rates between 3.8×10
−2 and 53 K/s, and besides
Pm sub-peak (
Ps) appeared above 323 K in the specimens which were cooled at the rate of 5.5 K/s or more.
With increasing cooling rates, the values of
Ps increased and the temperature of
Ps had a tendency to become lower. Curves of Young’s modulus and differential scanning calorimetry showed the minimum value and the maximum value respectively at the temperature appearing
Ps; showing that
Ps is the phase transformation peak.
The values of
Pm kept constant at the rate of 5.5 K/s or more after showing a linear increase with increasing cooling rate less than 5.5 K/s, where the values of
Pm depended on the contents of γ′ martensite, and the single phase of γ′ martensite could be obtained from the specimens cooled at the rates beyond 5.5 K/s.
From the above-mentioned considerations, it was suggested that the
Pm was the twin-boundary relaxation peak of γ′ martensite.
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