Quasicrystal-reinforced high strength Al-Mo-Si alloys

Powders obtained by gas atomization of high Al-content (90at.%) Al-Mn-Si alloys are found to contain nano-and micrometer sized quasicrystal precipitates which strongly enhance the tensile strength of the Al-Mn-Si alloy when extruded. The quasicrystal content in the powders increases with Mn-content, with highest volume fractions obtained for Al93Mn6Si1: here powders above 10 mu m in diameter have a 40 vol.% quasicrystal content of mostly icosahedral 'flower-shaped' Al85Mn15 microquasicrystals, whereas powders below 10 mu m in size contain 50 vol.% 'granular'-shaped five-fold Al85Mn14Si1 nanoquasicrystals. The quasicrystalline phase is retained upon extrusion of the powders and an increase in tensile strength with increasing quasicrystal content and decreasing quasicrystal size is observed for all bulk Al-Mn-Si alloys. Highest tensile strength in combination with good elongation is obtained for Al93Mn5Si2 alloy derived from <25 mu m sized powders (sigma(b) = 486 MPa, sigma(0.2%) = 436 MPa, E = 83 GPa, epsilon = 20%, H-v = 144). Standard powder-metallurgy processes can be applied to the quasicrystal-reinforced Al-Mn-Si alloys and they are expected to pose a cheaper alternative to other particle or fibre reinforced Al alloys.