High-strength aluminum- and zirconium-based alloys containing nanoquasicrystalline particles

By the dispersion of nanoscale quasicrystalline (Q) particles in f.c.c.-Al or Zr-based glassy phase, new Al- and Zr-based alloys with good mechanical properties were developed in a high Al content range of 93-95 at.% of Al-Cr(or Mn)-Co-Ce, Al-Mn-Co-Cu and Al-Cr-Fe-Ti systems and in Zr65Al7.5Ni10Cu17.5-xMx (M = Ag or Pd; x = 5 and 10 at.%) systems. The structure consists of Q-particles with a size of 30-50 nm surrounded by Al with a thickness of 5-10 nm for the Al-based alloys and Q-particles with a size of about 30 nm surrounded by glassy phase with a thickness of less than 1 nm for the Zr-based alloys. The Q-phase has high volume fractions (V-f) of 60-70% for the former alloys and 80-90% fur the latter alloys. The former structure is formed by the solidification mode in which the Q-phase precipitates as a primary phase, followed by precipitation of Al from the remaining liquid. The latter structure results from homogeneous nucleation and slow growth from the glassy phase. The high V-f of the Q-particles is presumably due to the existence of randomly oriented icosahedral clusters in the supercooled liquid of the Al- and Zr-based alloys. The features of mechanical properties are classified into four types, i.e., high-strength type of 800 MPa in Al-(Mn, Cr)-Ce-Co systems, high elongation type of 30% in Al-Mn-Co-Cu system, high-elevated temperature strength type of 350 MPa at 573 K in Al-Fe-Cr-Ti system, and high-strength type of 1900 MPa in the Zr-based system. These mechanical properties are promising for the future extension of the new Al- and Zr based alloys to practical materials. (C) 2000 Published by Elsevier Science B.V.