FORMATION OF QUASI-CRYSTALLINE AND AMORPHOUS PHASES IN MECHANICALLY ALLOYED AL-BASED AND TI-NI-BASED ALLOYS

The formation of quasicrystalline and amorphous powders by mechanical alloying from crystalline, elemental powders has been investigated for Al-Cu-M (M = V, Cr, Fe, Co, Ni), Al-M-Si (M = Cr, Mn), Al-M (M = V, Cr, Mn, Fe, Co), Ti-Ni-Fe-Si, and Ti-Ni-V alloy systems. The alloying process has been monitored by X-ray diffraction and differential scanning calorimetry, and the microstructure has been characterized by scanning electron microscopy. Quasicrystalline phases form directly during milling by a solid-state interdiffusion reaction from the crystalline starting materials for Al-Cu-Cr and Al-Cu-V. For Al-Cu-Fe the formation of the quasicrystalline phase is observed after additional annealing at elevated temperatures. Amorphous phase formation is achieved for the Ti-Ni-Fe-Si, Ti-Ni-V, Al-M-Si (M = Cr, Mn), and Al-M (M = V, Fe) alloy systems. For Ti-Ni-Fe-Si and Al-Cr-Si additional annealing results in an amorphous-to-quasicrystal transition. Finally, no alloying during milling has been obtained for binary Al-Mn, Al-Co, and Al-Cr. Only for Al-Cr the formation of a quasicrystalline alloy can be observed after isothermal annealing of the layered composite formed during milling. The results are compared with data for rapidly quenched material.