13th International Conference on Fracture June 16–21, 2013, Beijing, China -4- indicates that gallium is in liquid phase when the specimen fails. At 423 K, in spite of large maximum stress and fracture strain, the optical micrograph shows that reduction of cross-sectional area does not localize and the fracture surface is rough, which is different from the typical ductile fracture surface. 4. Discussion In Fig. 3 we showed that the ductility trough exists as a function of temperature in polycrystalline silver-liquid gallium couple. We have reported in [7] that for this couple the recovery from LME is observed if the contact time between the solid and liquid metals is long. In [7] the tensile test was performed at 308 K on the specimens with 10 mg of gallium after they were kept in a furnace at the temperature Th for certain holding times th. Stress-strain curves are shown in Fig. 5(a) for the specimens of Th =373 K. In Fig. Figure 4. Scanning micrograph of the fracture surface (upper) and optical micrograph of the specimen (lower) tested at (a) 398 K, (b) 413 K, (c) 423K and (d) 465 K.
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