Icosahedral single quasi-crystals were deformed, at temperatures between ambient and 400C, by means of Vickers hardness testing. After room-temperature tests, a polygrain microstructure was found which suggested the occurrence of deformation via grain-boundary glide. At high temperatures, fragmentation as well as dislocation formation were observed. After deformation at 200C, stacking-like faults were visible. The normal of the habit plane of these features was always parallel to one of the 2-fold axes of the quasi-crystal. Decagonal precipitates were therefore eliminated from consideration because they were known to grow parallel to the 5-fold planes. They were instead interpreted as being phason walls which were introduced, during deformation, in the wake of moving dislocations. The velocity of the dislocations was believed to be insufficient to mediate plastic deformation at the macroscopic scale.

Microstructural Investigation of the Brittle-to-Ductile Transition in Al-Pd-Mn Quasicrystals. M.Wollgarten, H.Saka, A.Inoue: Philosophical Magazine A, 1999, 79[9], 2195-208