Papers by Author: V.A. Ivanov

Abstract: A new method is introduced to determine the absolute value of the boundary excess free volume. Along with the boundary energy the excess free volume belongs to the major thermodynamic properties of grain boundaries. The method utilizes the dependence of the contact angle at triple junctions of grain boundaries in Al-tricrystals on hydrostatic pressure. We investigated <111> tilt boundaries in the pressure range up to 14 kbar. In particular, for a 40° <111> tilt boundary with 2° twist component the boundary free volume was found to be equal to 5.03×10-11 m3/m2.

Abstract: The motion of a curved grain boundary with a “surface triple junction” (“free surface – boundary - free surface”) in aluminum bicrystals is studied. The effect of the “surface triple junction” on grain boundary motion is discussed in the terms of the equilibrium of boundary and junction velocity. Boundary motion in samples with different boundary curvature revealed a strict proportionality of boundary velocity and driving force. This result corroborates the fact that in the entire investigated temperature range the “surface” triple junction does not affect the boundary motion.

Abstract: The motion of <111> tilt and mixed tilt-twist grain boundaries with misorientation angles in the range between 34° and 42° in pure Al bicrystals was measured over the temperature range between 310 and 610°C. The experiments revealed that the change of the set of boundary planes in the curved moving tilt boundary does not affect its motion. The shape of the curved moving part of the mixed tilt-twist boundary was measured and compared with analytically calculated boundary shape. The results have shown that an increase of the twist component along the curved mixed boundary in studied geometrical configuration does not affect its steady-state motion. Similar to the behaviour of <111> pure tilt boundaries, the mobility of <111> mixed tilt-twist grain boundaries in the vicinity of special misorientation å7 depends on the misorientation angle in a non-monotonic fashion.