Microstructure and wear behavior of quasicrystalline thermal sprayed

An Al-Cu-Fe alloy coating which forms a quasicrystalline phase is a potential candidate for replacing electro-deposited chromium on various components in the Space Shuttle Main Engine. Coatings were deposited by air and vacuum plasma spraying and by high-velocity oxygen-fuel spraying. Finer starting powders tended to lose Al during spraying, which affected the phase equilibrium of the coatings. Coatings which retained the starting powder composition were richer in the desired quasicrystalline phase. Ball-on-disk wear tests between 440 C stainless steel ball and the Al-Cu-Fe coatings were performed. Coefficients of friction ranged from 0.60 to 1.2 for the different coatings

Quasicrystalline particulate reinforced aluminum composite

Particulate reinforced aluminum and aluminum alloy composites are rapidly emerging as new commercial materials for aerospace, automotive, electronic packaging and other high performance applications. However, their low processing ductility and difficulty in recyclability have been the key concern. In this study, two composite systems having the same aluminum alloy matrix, one reinforced with quasicrystals and the other reinforced with the conventional SiC reinforcements were produced with identical processing routes. Their processing characteristics and tensile mechanical properties were compared

Pulsed laser ablation of Al-Cu-Fe quasicrystals

Quasicrystalline Al65–Cu23–Fe12 targets have been ablated by a doubled Nd:YAG laser and deposited on silicon substrates. The results show evidence of distinct ablation mechanisms, which lead to different gas phase composition, as a function of the laser fluence. Films containing the quasicrystalline phase can be deposited only at fluences higher than about 6.5 J/cm2 while at lower fluences the aluminium content exceeds the stoichiometric value. The films obtained by laser ablation of quasicrystalline Al65–Cu23–Fe12 were compared with those obtained from the metallic alloy Al70–Cu20–Fe10. The differences between the two systems could be explained on the basis of the low thermal conductivity of the quasicrystalline phase

Deformation behavior of an amorphous Cu64.5Zr35.5 alloy: A combined computer simulation and experimental study

Molecular dynamics (MD) simulations were performed to examine the temperature-dependent elastic properties and high-temperature deformation behavior of a Cu64.5Zr35.5 amorphous alloy. From the simulations we find that the elastic constants of the amorphous solid and supercooled liquid exhibit an approximately linear temperature dependence. The predicted temperature dependence of the Young's modulus for the amorphous solid obtained from the MD simulations is in good agreement with experimental measurements using dynamic mechanical analysis. Furthermore, the high-temperature plastic deformation behavior determined by MD simulations is qualitatively in good agreement with results from plastic deformation experiments performed on 1 mm diameter Cu64.5Zr35.5 metallic glass rods at 698 K. Notably, the MD simulations reveal that the flow softening regime of the stress-strain curve corresponds to an increase in the free volume in the atomic structure. Moreover, the simulations indicate that the atomic mobility significantly increases within the same regime