PHASON STRAINS ON GROWTH, STABILITY AND STRUCTURE OF ICOSAHEDRAL PHASES

Growth, stability and structure of icosahedral (i-) phases have been s tudied by electron diffraction and X-ray diffraction in relation with the phason strains. Three alloy systems; AlPdCr, AlPdMn and AlCuV were chosen in this study. An i-Al72Pd25Cr3 grain has been analysed to hav e a phason matrix toward to a tetragonal or orthorhombic structure. St ability of the i-phases correlated with the phason relaxation was disc ussed in Al-Pd-Mn system. A quenched i-Al74Pd17Mn9 close to but contai ning significant phason strains, revealed that the phason relaxation i nduced by precipitation of crystalline phases upon annealing. Phason d isorder dominated by the chemical composition was evidenced in a compo sition study in Al-Pd-Mn system. A high density random phasons charact erized the icosahedral glass phase was observed in AlCuV alloys.