Comparative study of microstructural influence on corrosion resistance in conventional and Al-Mn quasicrystalline cast aluminum alloys

The investigation focused on the quasicrystalline aluminum alloy Al-Mn-Cu-Mg-Si-Ti. The influence of microstructure of aluminum alloy strengthened with quasicrystals on its corrosion resistance was studied. The properties of newly designed quasicrystalline aluminum alloy (QC) were compared to the properties of standard AlSi9Cu3 alloy (DIN 226). Both aluminum alloys (QC and AlSi9Cu3) were cast in a steel die with a controlled cooling rate. After the preparation of the samples, the microstructural characterization was carried out. In the quasicrystalline alloy, the microstructure was dominated by a primary phase with fivefold symmetry, representing the quasicrystalline phase. To investigate corrosion properties, open-circuit potential, linear polarization and potentiodynamic polarization measurements were performed. The influence of corrosion on mechanical properties was studied by conducting tensile tests on environmentally exposed alloys. It was concluded that the quasicrystalline alloy has comparable corrosion properties to the commercially widely used AlSi9Cu3 alloy. In the latter alloy, corrosion was observed to initiate in the vicinity of the Al$_2$Cu intermetallic compound particles. In the case of the QC alloy, corrosion attacked mainly the α$_{Al}$ phase (matrix).