The deposition of nanoscale multilayer films allows to circumvent thermodynamic restrictions in equilibrium bulk conditions to generate supersaturated aluminide phases in thin films outside the phase boundaries in a subsequent heat-treatment. It can be successfully shown that the phase formation of the cubic B2 structure can be realized in the ternary systems (Rux, Me1-x)Al (Me=Hf and Cr) in different compositions by a targeted multilayer design. The resulting microstructure influences the mechanical properties as well as the corrosion resistance and shows significant improvements compared to directly deposited RuAl single layer thin films. The correlation between the thin films’ microstructure before and after a thermal heat treatment and the respective mechanical properties are investigated. The phase formation is observed by HT-in-situ-XRD, while the mechanical properties as well as the microstructure are examined by microindentation and TEM analysis respectively.
It can be successfully demonstrated that the phase formation of ternary aluminides in the B2 structure can be specifically adjusted using a suitable nanoscale multilayer system allowing the formation of metastable single-phase TM-aluminides. The layer morphology thereby significantly influences the phase formation and suppresses the formation of stable complex intermetallic phases. As a result, new materials with adjustable microstructure and resulting mechanical and corrosion-reducing properties can be synthesized.