Quasi-crystals and their crystalline homologues in the Al60Mn11Ni4 ternary alloy

SUMMARY The transition quasi-crystallinecrystalline is found to be very sluggish in the ternary alloy Al60Mn11Ni4. This makes it possible to study in detail the relationship between the decagonal phase, obtained after furnace cooling, and two different crystalline phases, which result after long annealing at 400°C. Use is made of electron diffraction, high resolution electron microscopy and optical diffraction. The crystalline phases still exhibit features which are closely related to those of the decagonal phase. This can be concluded from a comparison of the electron diffraction patterns of the quasi-crystalline phase along a number of zones, with those of the crystalline phases along corresponding zones. The crystalline phases contain different types of defects which are analysed in detail using high resolution images and diffuse scattering in the electron diffraction patterns. The close relationship between the electron diffraction patterns of the crystalline and quasi-crystalline phases is explained in terms of general optical principles. Some characteristic features of a model of the quasi-crystalline phase are tentatively proposed.