Caracterização microestrutural e tribológica de compósito em matriz de alumínio reforçado com quasicristais do sistema Al-Cu-Fe-Cr obtido através de solidificação (in situ)

Abstract

Quasicrystals, their properties and the manufacturing processes involved in their fabrication have been studied in recent decades, in order to find possible practical applications of these materials in the industry. The AlCuFeCr system is one of the most studied systems nowadays due to the presence of the stable decagonal quasicrystalline phase observed in the alloys of this system. However, as high cooling rates are still requires in most of the known fabrication processes for these materials and the brittle behavior presented by these materials make it, currently, impossible their applications. In this study, a bulk form of an aluminum alloy with Al85Cu6Fe3Cr6 composition was manufactured by spray-forming, carried out in a single manufacturing step. Gas atomized particles and a arc-melted bulk sample were also analyzed. A microstructural characterization of the alloy revealed a presence of the quasicrystalline decagonal stable phase in equilibrium with intermetallic phases and face centered cubic aluminum (FCC). This work produced, for the first time, a large volume (> 1 kg) Al-matrix composite reinforced with quasicrystals, through a single-step solidification process. Phase formation sequence is different when comparing the arc-melted sample and the gasatomized/spray-formed samples. While the arc-melted sample requires a posterior thermal treatment to increase quasicrystalline phase fraction, the gas-atomized or spray-formed samples formed a large fraction of quasicrystal directly during the solidification process. This microstructural combination of quasicrystals with aluminum FCC showed to be effective for a good performance under sliding wear conditions, being significantly superior to a Al-Si A380 alloy in most tested conditions.