Lamellar structure and nanomechanical properties of quasicrystalline Al-Cu-Fe alloys

Abstract

Abstract-The kinetics of structural phase transformations in quasicrystal forming Al-Cu-Fe alloys with compositions in the region of stability of the icosahedral (i) phase has been investigated. It has been shown that, depending on the development of metastable transformations i pentagonal phases P1 and P2, a homogeneous lamellar structure (i + P1 + P2) or a polygrain i phase is formed in the alloys. The P-h dia grams obtained upon nanoindentation, atomic force microscopy, and scanning electron microscopy of indentations have demonstrated signs of elasto plastic deformation of the alloys with lamellar and polygrain icosahedral structures. It has been found that, in contrast to the polygrain icosahedral alloys with a normal size effect of nanoindentation, the alloys with a lamellar structure are characterized by a nonmonotonic dependence of the hardness (H) on the maximum load (P max ) and exhibit the effect of strain hardening in the range of loads 50 mN ≤ P max < 500 mN. The strain hardening is considered as the result of resistance exerted by boundaries of the lamellar structure to the development of plastic deformation.