Tie Lines of the Grain Boundary Wetting Phase Transition in the Zn-Rich Part of the Zn-Sn Phase Diagram

Abstract

The temperature dependence of the contact angle θ at the intersection of Zn grain boundaries with Zn/liquid Zn-Sn boundaries have been studied. For this purpose, two Zn bicrystals were grown with {1000} tilt boundaries having misorientation angles of o=16° (small angle grain boundary) and o=60°. These boundaries possess different energies. The temperatures T w of the grain boundary wetting phase transition for these two boundaries were determined and the corresponding tie lines in the two-phase (Sn)+L field of the Zn-Sn phase diagram were constructed. Above T w the contact angle θ is 0° and a layer of liquid phase substitutes for the grain boundary. The temperature of the wetting transition (T w1 = 382±1°C) for the boundary with the high energy (o=60°) is lower than that (T w2 = 386.5±1°C) for the boundary with the low energy (o=16°). Above the temperature interval where all the grain boundaries become wetted, the solid phase may exist only as isolated single crystalline islands in the sea of melted phase.