First observation of a wetting phase transition in low-angle grain boundaries |
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Authors: | B B Straumal B S Bokshtein A B Straumal A L Petelin |
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Institution: | (1) Institute of Solid State Physics, Russian Academy of Sciences, Chernogolovka, Moscow region, 142432, Russia;(2) State Technological University “Moscow State Institute of Steel and Alloys,”, Leninskiĭ pr. 4, Moscow, 119049, Russia |
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Abstract: | The wetting phase transition at low-angle intercrystallite grain boundaries has been experimentally observed. In contrast to the high-angle grain boundaries with the misorientation angels θ > 15°, the low-angle grain boundaries (θ < 15°) are not continuous two-dimensional defects, but constitute a discrete wall (network) of lattice dislocations (edge and/or helical). The theory predicts that, depending on θ, either a continuous layer of the liquid phase or a wall (network) of microscopic liquid tubes on wetted dislocation nuclei is formed at completely wetted low-angle grain boundaries. It has been shown that the continuous liquid layers at low-angle grain boundaries in the Cu-Ag alloys appear at the temperature T wminL = 970°C, which is 180°C higher than the onset temperature T wmin = 790°C and 50°C lower than the finish temperature of the wetting phase transition at high-angle grain boundaries, T wmax = 1020°C. |
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