Abstract:
Our research efforts were focused on finding and developing quasicrystal-based (QC) alloys for structural applications. Numerous chemical compositions were tried out all of them being based on the Al-Mn system. A wide variety of methods and approaches was employed to synthesize, characterize, test and evaluate our alloys, especially LOM, SEM, EDS, EBSD, TEM, HRTEM, SAED, X-ray CT, DTA, DSC, XRD, Rietveld calculations, thermodynamic considerations, mechanical and nano-mechanical testing, and corrosion resistance assessment. More than twelve pure elements or their combinations were introduced into Al-Mn based alloys, but only some have proven to promote the formation of QCs, when sufficiently high cooling rates were employed. Furthermore, an introduction of modifiers into Al-Mn-based melts was also tested to assess their ability to ease the formation and growth of metastable QCs. We were able to show that QCs will grow in-situ during the solidification of the Al-Mn-based liquid alloy. This provided us with metal matrix-quasicrystal (MMQC) composite materials reaching Yield Strength (YS) up to 400 MPa, elongations in excess of 30 % and corrosion resistance comparable to that achievable in commercial 6XXX alloy series. Deformation behavior of macro-sized MMQC composites was also investigated, and the deformation mechanism in QC particles on the nano-scale was examined through in-situ nano-tensile and nano-compression experiments. QC particles as MMQC constituents have been shown to have the ability to undergo severe plastic deformation without forming cracks or cleavage. The introduction of various inoculants into the Al-Mn based melt proved to influence the formation of QCs during solidification of the melt by serving as a substrate for QCs to grow.
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