Ar-ion-milling-induced structural changes of Cu₅₀Zr₄₅Ti₅ metallic glass

We have systematically studied Ar-ion-milling-induced microstructural evolution in Cu₅₀Zr₄₅Ti₅ metallic glass (MG) during specimen preparation for transmission electron microscopy (TEM). We have observed the formation of a Cu₁₀Zr₇ intermetallic phase in samples prepared using low energy ion milling (2 keV) but without evident crystallization. We also observed the formation of nanocrystalline Cu₁₀Zr₇ phase (with a possibility of being mixed with other minor phases) in samples prepared using high energy ion milling (≥3 keV). In contrast, the MG samples remained in the glassy state without any microstructural changes when prepared by either electropolishing or low energy ion milling with liquid nitrogen cooling (2 keV). Further, our study suggests that chemical decomposition might be a necessary intermediate stage for crystallization. In situ TEM electron irradiation shows ion-milling-induced phase segregation and preferred nanocrystallization in the precipitated regions.