Structural relationship and mutual transformation of approximants of the decagonal Al–Co–Ni phase

Apart from the decagonal phase, several different approximant structures were observed in the Al–Co–Ni alloy system. In this work, specimens with a composition of Al71Co14.5Ni14.5 are investigated by conventional and high-resolution transmission electron microscopy. The structural relationships between two approximant phases are studied in detail. Simplified atomic models of these structures are derived from high-resolution electron microscopy and verified by image contrast simulation. A transition between the two approximants is possible by changing only a few atomic positions. Nevertheless, these minor changes are sufficient to produce rather striking changes in high-resolution electron microscopy images.