The role of lattice mismatch in heterogeneous nucleation of pure Al on Al2O3 single-crystal substrates with different termination planes

Abstract

Al solidification on Al2O3 single-crystal substrates with (0001) and (11 $$ \overline{2} $$ 0) termination surfaces was performed to investigate whether the lattice mismatch can influence the heterogeneous nucleation when the same kind of substrate was employed. Nucleation undercooling was measured via differential scanning calorimeter to present the nucleation potency of Al on selected substrates. The measured results show that the lower undercooling was achieved in Al/Al2O3(11 $$ \overline{2} $$ 0), which means that the Al has a higher nucleation potency on Al2O3(11 $$ \overline{2} $$ 0) substrates. This is consistent with the calculated lattice misfit of Al/Al2O3(0001) and Al/Al2O3(11 $$ \overline{2} $$ 0) based on Bramfitt two-dimensional model because the lowest lattice misfit of Al/Al2O3(11 $$ \overline{2} $$ 0) is less than that of Al/Al2O3(0001). Moreover, the corresponding orientation relationships at the interface achieved by high-resolution transmission electron microscopy are almost the same with the predicted one from lattice misfit calculation. It is proved that the lattice misfit does affect the heterogeneous nucleation even the melted metals nucleated on the substrates made of the same kind of material.