Philosophical Magazine a-Physics of Condensed Matter Structure Defects and Mechanical Properties
Complex structures can be regarded as bring derived from a few basic structures via the local twinning at the atomic level. Although quasicrystals and approximants are believed to be the B2 derivatives, the related B2 twinning mode is not known. This paper addresses this problem by analysing the twinning property of Al-Cu approximants in an Al3Cu4 sample. Such an analysis leads to the recognition of the B2 chemical-twinning mode as 180 degrees/[111]B-2, which is responsible for the pentagonal atomic configuration in the Al-Cu approximants as well as for the pseudofivefold B2 twinning observed on quasicrystal surfaces.
关键词:
quasi-crystals
Physica Status Solidi B-Basic Research
In an alloy with nominal composition of Al67Cr15Cu18 annealed at 900 degreesC and below, microdomains of decagonal approximants have been identified by means of transmission electron microscopy. High-resolution images show that the microdomains, whose electron diffraction patterns display almost perfect tenfold rotation symmetry, are composed of three crystalline approximants intergrown with each other. The crystallographic relationships between these phases are given; and phase transformation between decagonal quasicrystal and its approximants is discussed.
关键词:
quasi-crystals
