Variation of internal friction with time in metallic glasses near glass transition temperature

Internal friction (IF) of a bulk metallic glass Zr55Cu30Al10Ni5 has been measured near and below/above the glass transition temperature Tg. The specimen is prepared by rapid cooling the liquid mother alloy through casting into a copper ingot. The size of the specimen is about 30 mm × 2 mm × 0.8 mm. The amorphous state of the specimen is checked by the X-ray diffraction, and the temperatures of glass transition (Tg=666 K) and crystallization (Tx=746 K) are determined by the DSC method. The specimen is stabilized by annealing at Tg–10 K for 10 h. The IF measurement is performed by using DMA (TA Instrument) apparatus at the frequency of 0.1 Hz. The deformation mode of vibration is the cantilever bending. The specimen is kept at a constant temperature T, and the IF value Q−1 is measured as a function of duration time t( = 0∼2.5×104s). The temperature is controlled by the apparatus. The measurement is successively carried out at various temperatures T = (Tg−50K)∼(Tg+50K). The Q−1-vs-t behavior is different in ...