SYNTHESIS AND PROCESS CHARACTERIZATION OF MECHANICALLY ALLOYED ICOSAHEDRAL PHASE MG-ZN-AL

The formation process of the icosahedral i-Mg32 (Zn, Al)49 phase during mechanical alloying has been studied. In the case of synthesis of i-phase from the metal powder mixture, the intermediate amorphous phase appeared during the first stages of mechanical alloying. In contrast the transformation of the cubic Frank-Kasper phase into the icosahedral one, was accompanied by progressive broadening and disappearance of the Bragg's peaks of the cubic phase without amorphization. These observations are discussed in terms of the structural relations of the amorphous, icosahedral and cubic Frank-Kasper phases, the formation and packing of icosahedral clusters during mechanical alloying of the metal powder mixtures and, on the other hand, the distortion of the cubic phase due to the formation of line defects.