Dislocations in Al–Pd–Mn approximants: a high resolution electron microscopy study

In plastically deformed crystals of the ξ′-Al–Pd–Mn phase dislocations with different Burgers vectors were observed in a high-resolution electron microscopy (HREM) study. The Burgers vector magnitudes are equal to the physical space components of the Burgers vectors found in the icosahedral phase. In particular, they also show a scaling behavior in the approximant involving the golden mean τ. Through the orientation relationships between the icosahedral phase and the approximant we have found that the Burgers vector directions are equivalent in both phases. This is surprising as some of the Burgers vector directions do not correspond to any crystallographic orientation in the approximant crystal, indicating that local (icosahedral) order is more important to dislocations than long range (crystalline) order.