13th International Conference on Fracture June 16–21, 2013, Beijing, China -5- 5(b) the maximum stress is shown as a function of the holding time th. Ductility recovers around 80 ks. Figure 5(c) shows the recovery time tR as a function of the furnace temperature Th. The recovery observed in the time dependence is considered due to formation of ’-phase or Ag7Ga3 by the X-ray diffraction analysis. From Fig. 5(c), the recovery time of the specimen held at 465 K is estimated more than 10 ks, when it is stressed at 308 K. In the present experiment, however, the specimens stressed at 465 K is not embrittled, although the test was performed immediately after the specimen temperature became the test temperature, and the test ended in less than a few minutes. The specimen that is ductile at 465 K becomes brittle at 308 K. As shown in Fig. 4(d), the fracture surface of the specimen pulled at 465 K is covered with gallium flowing from the specimen surface. At this temperature the specimen Figure 5. (a) The stress-strain curves. After the specimens were kept in contact with a small amount of gallium at 373 K for the time indicated in the figure, the tensile testing was performed at 308 K with a strain rate of 1.2×10-2 s-1. (b) The maximum stress max as a function of holding time th. (c) The time to recover ductility tR as a function of the temperature of the furnace Th [7].
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