Nano-scale Shell in Phase Separating Gd-Ti-Al-Co Metallic Glass

Abstract

In the present study, formation of yard and shell has been investigated in as-melt-spun Gd30Ti25Al25Co20 alloy using a variety of transmission electron microscopy techniques. The phase separation during cooling leads to the formation of the microstructure consisting of amorphous droplets with different size scales embedded in the amorphous matrix. Due to the interdiffusion at the interface after the first-step phase separation, ~50 nm-thick yard develops on the surface of the primary droplet particle. Due to the critical wetting phenomenon, ~5 nm thickness shell enveloping the droplet forms. The sell is enriched in Co and Ti, implying that the composition is close to that of the droplet.