Laser Cladding of Aluminium-Base Quasicrystalline Alloys

F. AUDEBERT, R. COLAÇO, R. VILAR AND H. SIRKIN

SCRIPTA MATERIALIA

PERGAMON-ELSEVIER SCIENCE LTD

Año: 1999 vol. 40 p. 551 - 557

1359-6462

In the mid eighties, Shechtman et al. (1) observed a fivefold symmetry axis on electron diffraction patterns of an alloy of the Al-Mn system. Since, on one side, it is impossible to generate a completely periodic structure from a fivefold symmetry lattice but, on another side, the structure was highly ordered, the term ?Quasicrystal? was introduced then. Soon, quasicrystals were discovered in other alloy systems, namely in Al-base systems, in Ti-base systems and also in systems such as duplex stainless steel alloys (2). The atomic structure of quasicrystals present long range order but escape to the translation rules of crystallography and, in a certain sense, these materials can be considered a new form of condensed matter, somehow between the structure of crystals and the structure of glasses. Though there are different types of symmetries in quasicrystals, the two most important correspond to the icosahedral phase and to the decagonal phase. In a simple way it can be said that the decagonal phase is quasiperiodic in two dimensions and periodic in the third, while the icosahedral phase is quasiperiodic in three dimensions.