ИСТИНА

A short overview on the relationship between grain boundary (GB) misorientation and wettability in metallic systems is presented. Own experimental results obtained in a number of metallic systems (Pb/Ni, Ag/Ni, Sn/Zn, Ga/Zn) are discussed together with known literature data. The basic concept consists in the following: misorientation and plane orientation determines structure, and, consequently, the energy of grain boundary. Comparison of GB and solid/liquid energy allows to conclude if grain boundary wetting (gb  2sl) or equilibrium dihedral angle (gb < 2sl) will occur (Gibbs-Smith approach). Experimental approaches could be divided into free main groups with different advantages and drawbacks: 1. Specially grown bicrystals with well-defined orientation of grains and plane position are brought in contact with melt 2. Melt is deposited on the surface of polycrystals, 3. Two-component alloy is prepared and heated over the eutectic melting point. Morphology of grooves formed on the triple junction of GB and two solid-liquid interfaces could be revealed after quenching and consequent metallographic preparation. Such powerful tool as EBSD analysis allows fast determination of grain orientation in last two cases. Special methods such as dissolution of low-melting phase or 3-d X-ray tomography could be used to reveal microstructure of the sample. Due to complexity of general representation of GB geometry (macroscopic parameters are 3 degree of freedom for misorientation and 2 for boundary plane orientation) exhausting analysis of GB energy vs. misorientation did not complete to the moment even for the simplest case of cubic crystals. Thus the most part of experimental results are presented in form of correlation between one misorientation parameter (e.g. misorientation angle for the fixed rotation axis) and GB wettability parameter (could be a part of wetted GBs). Approaches for simple presentation of misorientation in hexagonal and tetragonal materials are presented. Different complications in use of simple Gibbs-Smith scheme are discussed. Grain boundary phase transitions, anisotropy of solid-liquid interfacial energy, grain boundary “prewetting” phenomena, size effects are among that complications.