Crystallization-induced phason relaxation in icosahedral Al-Pd-Mn alloys

A melt-quenched icosahedral ( i -) phase with a composition such as Al 74 Pd 17 Mn 9 close to but is deviated slightly from the ideal composition (Al 70 Pd 20 Mn 10 ) of stable i -AlPdMn alloy, containing significant phason strains. It transforms to a phason-free i -phase accompanied by crystallization upon annealing at sufficiently high temperature. The composition of the i -grains approaches the ideal after the transformation. Such phason strain relaxation was not observed in the melt-quenched Al 75 Pd 15 Mn 10 i -phase, for which composition considerably deviates from the ideal composition; crystallization occurs without redistribution in the composition. It was suggested that a highly stable i -phase occurs in the ground state when it has the ideal composition.