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Laser diffraction, Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD), Transmission Electron Microscopy (TEM) and Differential Scanning Calorimetry (DSC) were employed to characterize the particle size, morphology and structure of mechanically alloyed Ti50Al30Ni20 alloy. Cyclic amorphous-crystalline-amorphous phase transformations were investigated during mechanical alloying, using high-energy ball milling technique. After 20 h of milling, an amorphous/nanocrystalline phase was obtained. This amorphous/nanocrystalline phase tended to transform into crystalline grains after 50 h of milling. In a cyclic phase transformation, the obtained crystalline phase is transformed into the amorphous phase after 70 h of milling. This amorphous phase crystallized through a single sharp exothermic peak at 590°C. On the basis of our results, the destabilizing effect of the defects created by the milling media (balls), which leads to the cyclic transformations, depends on the input energy and milling time. |
