Grain boundary segregation and grain boundary wetting

We give an explanation of the phenomenon of a liquid film penetration along a grain boundary (GB) using a kinetic mechanism that does not rely a wet state of the GB. The mechanism is as follows. Fast diffusion of the liquid's atoms (LA) along a straight stationary GB induces its instability in concentration field of the LA and results in displacement of the GB. A high concentration of the LA can then be found in the area has been that swept by the GB. Due to its composition, this area has low melting temperature, and becomes liquid. The necessary thermodynamic condition for such a scenario is T-m(kc(lim)) < T-*, where T-m is the solid phase melting temperature depends on the LA concentration in the bulk, T. is the temperature in the experiment, k is the GB segregation coefficient, c(lim) is solubility limit of the LA in the solid matrix at T = T-*. We assume fast mass transport in the melt, and formulate a set of kinetic equations describing the process. Our solution describes the linear growth of a thin channel filled with liquid.