Phase transformation induced by irradiating an Al₆₂Cu_25.5Fe_12.5 icosahedral quasicrystal

The irradiation effect of the Al₆₂Cu_25.5Fe_12.5 icosahedral quasicrystal (IQC) induced by 120 keV Ar ions and 1 MeV electrons has been studied in situ using high-voltage electron microscope-ion accelerator dual-irradiation facilities. The effect is dose and temperature dependent and we can define three critical temperatures T_c, T_d and T_p. When irradiated at T<T_c the IQC is transformed into a crystalline microtwin oriented according to icosahedral symmetry. When T>T_c, the IQC remains an IQC but with a higher (when T>T_d) or lower (when T<T_d) degree of perfection. The planar defects originally existing in the Al₆₂Cu_25.5Fe_12.5 IQC foils are stable when T>T_p but disappear when T<T_p. For the Al₆₂Cu_25.5Fe_12.5 IQC, we found that T_c approximately=400 K, T_d approximately=450 K (for 1 MeV electrons) or 550 K (for 120 keV Ar ions) and T_p approximately=600 K.