Stability of nanocrystallites dispersed in Cu ₅₀Zr ₄₅Ti ₅ metallic glass under electron irradiation

Effect of electron irradiation on stability of nanocrystallites dispersed in a glassy matrix of a Cu ₅₀Zr ₄₅Ti ₅ bulk metallic glass (BMG) alloy was investigated. Microstructural evolution during electron irradiation was observed and analyzed by means of conventional and high-resolution transmission electron microscopy (CTEM and HRTEM) and X-ray energy dispersive spectroscopy (EDS). The crystalline nanoparticles of monoclinic CuZr phase formed in-situ in as-cast Cu ₅₀Zr ₄₅Ti ₅ alloy exhibited a high stability against electron irradiation. No obvious changes in their size, morphology, and crystal structure were observed during electron irradiation, though new crystalline nanoparticles nucleated and precipitated in the glassy matrix under electron irradiation. The new nanoparticles formed upon irradiation have a similar composition and crystal structure to those formed in-situ in the as-cast alloy. The nanocrystalline precipitates in the glassy matrix are proposed to be mainly due to electron knock-on effect under electron irradiation, which promotes atomic diffusion and assists the crystallization of the glassy phase. The present result indicates that electron irradiation to metallic glasses has potential for producing nanocrystalline structure and nanocrystalline-glassy composite structure.