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

Abstract

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 93–95at.% 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 10at.%) systems. The structure consists of Q-particles with a size of 30–50nm surrounded by Al with a thickness of 5–10nm for the Al-based alloys and Q-particles with a size of about 30nm surrounded by glassy phase with a thickness of less than 1nm for the Zr-based alloys. The Q-phase has high volume fractions (Vf) of 60–70% for the former alloys and 80–90% for 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 Vf 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 800MPa in Al–(Mn, Cr)–Ce–Co systems, high elongation type of 30% in Al–Mn–Co–Cu system, high-elevated temperature strength type of 350MPa at 573K in Al–Fe–Cr–Ti system, and high-strength type of 1900MPa 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.