Ordered nanocrystal formation in Cu_(50)Zr_(45)Ti_5 metallic glass

摘要

The paper reports formation of ordered nanocrystals in amorphous Cu50Zr45Ti5 metallic glass (MG) when exposed to ions in focused ion beam (FIB) instrument. The specimen was subjected to 30 keV Ga ion beam during trenching, lift out of a lamella, and thinning to a thickness of about 100 nm. Transmission electron microscopy confirms formation of ordered nanocrystals 2-5 nm In size, aligned along lines, which have similar to 10 nm separation distance. It is hypothesized that solid flow induced by ion bombardment leads to ripple formation. The diffusible short-range order quasicrystals agglomerate in the crest regions under stress and the agglomeration is followed by local nanocrystal nucleation. The FIB process is unable to induce such an ordered nanocrystal matrix in MG Ti40Cu31Pd14Zr10Sn2Si3. The difference in radiation resistance is explained by the level of complexity in the correlated diffusion needed for crystal nucleation, which is reflected by the width of the supercooled liquid region.