AbstractA stable Al65Cu20Fe15quasicrystal with an icosahedral structure is studied in solid and liquid state. It is found that the icosahedral phase in Al65Cu20Fe15alloy does not grow directly from the pure liquid state, but rather forms between monoclinic Al13Fe4and residual liquid state at 865 °C. The melting point of the Al65Cu20Fe15icosahedral quasicrystal occurs at 865 °C and that of the Al65Cu20Fe15alloy occurs at 1008 °C. Moreover, the monoclinic Al13Fe4is transformed into the icosahedral phase easily at the temperature of 845 °C. The icosahedral quasicrystal in Al65Cu20Fe15alloy has a high thermal stability even at 950 °C. Above 950 °C, the icosahedral structure tends to an amorphous stru