The microprocesses of the quasicrystalline transformation in Zr₆₅ Ni₁₀ Cu₇.₅Al₇.₅Ag ₁₀ bulk metallic glass

Abstract

The microprocesses of the amorphous-to-quasicrystalline transformation in Zr₆₅ Ni₁₀ Cu₇.₅Al₇.₅Ag ₁₀ bulk metallic glass were studied in detail by transmission electron microscopy (TEM) and high-resolution TEM (HRTEM). It was found that the amorphous-to-quasicrystalline transformation in the present system undergoes a series of interprocesses and follows the sequence of the phase transformation of amorphous →FCC Zr₂Ni→Tetragonal Zr₂Ni→Tetragonal Zr₂Ni with a domain structure →Quasicrystals. HRTEM indicated that a domain structure with a high density of stacking faults was formed in the sample at the stage just prior to the formation of quasicrystals. This special structure seems to possess the structural symmetries similar to those of icosahedral quasicrystals. Nanobeam energy dispersive x-ray spectrum revealed that atomic diffusion was involved in all interprocesses of the phase transformations. This suggests that the amorphous-to-quasicrystalline transformation in the present bulk metallic glass is a nonpolymorphous reaction.