PHASE-TRANSFORMATION INDUCED BY IRRADIATING AN AL62CU25.5FE12.5 ICOSAHEDRAL QUASI-CRYSTAL

The irradiation effect of the Al62Cu25.5Fe12.5 icosahedral quasicrysta l (IQC) induced by 120 keV Ar ions and 1 MeV electrons has been studie d in situ using high-voltage electron microscope-ion accelerator dual- irradiation facilities. The effect is dose and temperature dependent a nd we can define three critical temperatures T-c, T-d and T-p. When ir radiated at T < T-c, the IQC is transformed into a crystalline microtw in oriented according to icosahedral symmetry. When T > T-c, the IQC r emains 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 A 1(62)Cu(25.5)Fe(12.5) IQC foils are stable when T > T-p but disappear when T < T-p. For the Al62CU25.5Fe12.5 IQC, We found that T-c similar or equal to 400 K, T-d similar or equal to 450 K (for I MeV electrons) or 550 K (for 120 keV Ar ions) and T-p similar or equal to 600 K.