Desenvolvimento de novas ligas quasicristalinas à base de alumínio

Abstract

Quasicrystalline phases are known for presenting particular crystallographic characteristics that make them a separate group of solid materials. Most of these phases are Al-based and they form in compositions near complex intermetallic phases. Many of these intermetallic phases are called quasicrystalline approximants due to the similarity of their atomic structures. This work presents the development of quasicrystal-forming alloys, which have low friction coefficient and low surface adhesion energy, aiming to discover new quasicrystal compositions. Fabrication of quasicrystalline alloys was performed by starting from known quasicrystal compositions and then modifying them by the addition of elements that could potentially enhance corrosion resistance such as Cr and Ni. Arc melting and melt spinning were used in the fabrication of these alloys. The metallic system that showed to be more suitable for obtaining the quasicrystalline phase, Al-Cu-Fe-Cr, was selected for a detailed study using combinatorial approaches for fabrication and characterization of alloys so the composition range where the quasicrystal forms in this system could be found. This strategy makes use of advanced techniques such as magnetron co-sputtering and high-throughput X-ray diffraction and energy dispersive X-ray spectroscopy. One of the quasicrystalline alloys was selected and fabricated by atomization, followed to thermal spraying by High Velocity Oxygen Fuel to manufacture coatings, which were studied regarding phase formation and stability as well as wear behavior and surface adhesion energy. This coating fabricated with a new composition showed the formation of quasicrystalline phases as expected. Surface properties such as low coefficient of friction and low surface adhesion energy were observed in the samples.