Wetting and reaction of MgO single crystals by molten Al at 1073–1473 K

The wetting and reaction of molten Al on three different faces of MgO single crystals, (1 0 0), (1 1 0) and (1 1 1), at 1073–1473 K in a reduced Ar–3% H2 atmosphere were investigated using an improved sessile drop method. The wettability depends significantly on neither the substrate orientation nor the temperature under the aforementioned conditions. The intrinsic contact angles are possibly between 90 and 105. The reaction layer depth does not considerably vary with the MgO substrate orientation as well. The final reaction products are primarily a-Al2O3 phase for (1 0 0)MgO and j 0 -, j- and d-Al2O3 phases for (1 1 0) and (1 1 1)MgO, without a pronounced MgAl2O4 phase. The reactive wetting kinetics is characterized by three representative stages. The reasons for the weak dependence of the wettability on the MgO substrate crystallographic orientation and the effect of the reaction on the wetting are presented.