13th International Conference on Fracture June 16–21, 2013, Beijing, China -2- trough as a function of temperature and that as a function of time. 2. Experimental The tensile specimens used in this investigation is shown in Fig. 1. They were cut out from a silver plate of 99.98 % purity by electrodischarge machining. After mechanical polishing, the specimens were annealed at 1073 K for 2 hours. The average grain size of the specimens was 0.3 mm. A small amount of liquid gallium, 10 mg in weight and saturated with silver at 308 K, was deposited on the specimen, so that one of the four faces of the gauge section was completely covered with the gallium. To ensure the contact between the solid specimen and the liquid, the surface covered with liquid gallium was scratched with a needle. After immersing the specimen in liquid nitrogen to freeze the gallium, the specimen was placed in the tensile machine. The tensile test was performed on the specimen in a hot silicone oil bath in the temperature between 300 K and 465 K and in water between 274 K and 300 K. The strain rate was 1.2×10-2 s-1. The fracture surface was observed by the scanning electron micrograph (SEM). Fig. 1 Tensile specimen. The thickness is 2 mm. Figure 2. Stress-strain curves of silver specimen with gallium (solid lines) and without gallium (dashed lines). The test temperature is shown in the figure.
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