Formation and structure of icosahedral and glassy phases in melt-spun Al-Si-Mn

Abstract

X-ray scattering and electron-transmission microscopy of melt-spun Al-Si-Mn alloys reveal that the Al-Mn icosahedral phase itself can grow congruently over a range of composition varying from 16 to 20 at.?Mn, and Si atoms substitute Al atoms selectively. The Q dependences of linewidth \ensuremath{\Delta}Q suggest that Hendrick-Teller disorder is dominant; however, the conventional disorders are also present. The glassy Al-Si-Mn alloys show a pronounced prepeak at ${Q}_{p}$\ensuremath{\approxeq}1.6 A${\r{}}^{\mathrm{\ensuremath{-}}1}$ and a marked shoulder at the low-Q side of the main peak (Q\ensuremath{\approxeq}3.0 A${\r{}}^{\mathrm{\ensuremath{-}}1}$), suggesting a strong chemical order persisting in the crystalline intermetallic phases.