The formation condition of a stable Cu–Ga–Mg–Sc icosahedral quasicrystal

Abstract The formation condition and the stability of the Cu–Ga–Mg–Sc icosahedral quasicrystal have been investigated in terms of the effects of Mg concentration and long time annealing. An addition of a few percent of Mg to the Cu3.7Ga2.3Sc-type cubic approximant causes the formation of an icosahedral quasicrystal. This quasicrystal is formed near the alloy composition of Cu48Ga34Mg3Sc15, and is regarded as a thermodynamically stable phase since the amount of the icosahedral quasicrystal in the alloy increased by annealing at 770 °C. The structural quality of the quasicrystal was also improved by this annealing, and this improvement is related to the elimination or the reduction of quenched-in phason strains.