Tie lines of the grain boundary wetting phase transition in the Al-Sn System

Abstract

Temperature dependencies of contact angles θ at the intersection of grain boundaries in Al bicrystals with solid Al/liquid Al-Sn interphase boundaries were studied. For this purpose, two Al bicrystals were grown with tilt {001} grain boundaries having misorientation angles 9 = 38.5‡ (near 19 coincidence misorientation) and ϕp = 32‡. These boundaries possess different energies. The tempera-turesTw of the grain boundary wetting phase transition for these two boundaries were determined, and the corresponding conodes in the two-phase area of the Al-Sn phase diagram were constructed. AboveTw, the contact angle θ = 0 and a layer of the liquid phase completely wets the grain boundary. The temperature of wetting transitionTw1= 6047± 1 ‡C, for the grain boundary with high energy (ϕp = 32‡) is lower thanTw2 = 6177 ± 1 ‡C for the grain boundary with low energy (ϕ = 38.5‡). 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.