内部摩擦の振幅依存性によるアルミニウム薄膜の力学物性の評価

抄録

Amplitude-dependent internal friction in aluminum films on oxidized silicon substrates has been investigated by the free-decay method of resonant flexural vibration. According to the constitutive equation, the internal friction in aluminum films can be evaluated separately from the measured data on the film/substrate composites. The internal friction in aluminum films is considerably reduced after heat treatment between 620 and 720 K. In the annealed state, the amplitude-independent part decreases as the film thickness decreases, while the amplitude-dependent part shifts to a higher strain. On the basis of the microplasticity theory, the amplitude-dependent internal friction can be converted into the plastic strain as a function of effective stress. The stress-strain responses thus obtained for aluminum films show that the plastic strain of about 0.01% of the total strain increases nonlinearly with increasing stress. These curves tend to shift to a higher stress with decreasing film thickness. It is found that the microflow stress is inversely proportional to the film thickness, provided the grain size is larger than the film thickness.